Agarases are hydrolytic enzymes that act on the hydrolysis of agar and have a broad range of applications in food,cosmetics and pharmaceutical industries. In this study, a glycerol feeding strategy based on induction ...Agarases are hydrolytic enzymes that act on the hydrolysis of agar and have a broad range of applications in food,cosmetics and pharmaceutical industries. In this study, a glycerol feeding strategy based on induction mode optimization for high cell density and β-agarase production was established, which could effectively control acetate yield. First, exponential feeding strategy of glycerol with different overall specific growth rates（μ） was applied in the pre-induction phase. The results showed that the low μ（μ=0.2） was suggested to be the optimal for cell growth and β-agarase production. Second, the effects of induction temperature and the inducer concentration on cell growth and β-agarase production were investigated in the post-induction phase. When induced by isopropyl-β-d-thiogalactoside（IPTG）, the strategy of 0.8 mmol/L IPTG induction at 20℃ was found to be optimal for β-agarase production. When cultivation was induced by continuous lactose feeding strategy of 1.0 g/（L·h）, the β-agarase activity reached 112.5 U/mL, which represented the highest β-agarase production to date.Furthermore, the β-agarase was capable of degrading G. lemaneiformis powder directly to produce neoagarooligosaccharide, and the hydrolysates were neoagarotetraose（NA4） and neoagarohexaose（NA6）. The overall research may be useful for the industrial production and application of β-agarase.展开更多
This study was conducted to valorize four sources of fiber (Gliricidia sepium, Leucaena leucocephala, Moringa oleifera and palm nut fibers) in animal production. The experiments were carried out on 128 rabbits divided...This study was conducted to valorize four sources of fiber (Gliricidia sepium, Leucaena leucocephala, Moringa oleifera and palm nut fibers) in animal production. The experiments were carried out on 128 rabbits divided into 4 batches of 32 animals, reared for 8 weeks under the same conditions. Each batch was subdivided into two subgroups, one fed with a complete diet (a diet containing one of the fiber sources and served all day) and the other with the same diet separated from the fiber source (served at 9 a.m. and supplemented with the fiber source at 4 p.m.). Eight (8) experimental rations were, respectively, tested on the subgroups: complete feed Gliricidia sepium (CFG);supplemented feed Gliricidia sepium (SFG);complete feed Leucaena leucocephala (CFL);supplemented feed Leucaena leucocephala (SFL);complete feed Moringa oleifera (CFM);supplemented feed Moringa oleifera (SFM);complete feed palm nut fiber (CFF);supplemented feed palm nut fiber (SFF). In each subgroup, 4 rabbits were slaughtered at 15 weeks of age for a total of 32 rabbits. Physico-chemical parameters were evaluated on the feed and the meat. Data were analyzed using SAS 2013 software. Fiber content was similar (p > 0.05) for complete feeds. Fat content was high (p < 0.001) for the palm nuts fiber (27.34%) and the CFF feed (11.36%). Feeding rabbits with G. sepium leaves or palm nut fiber continuously increased the fat content of the meat in contrast to sequential feeding. Meat quality was also better when the fiber source was used in the feed of the rabbits in the evening.展开更多
The feeding method of propionic acid for production ofpoly(3-hydroxybutyrate-co-3-hydro xyvalerate) [P(3HB-co-3HV)] by fed-batch culture of Ralstoniaeutropha was optimized to achieve high cell density and high 3HV yie...The feeding method of propionic acid for production ofpoly(3-hydroxybutyrate-co-3-hydro xyvalerate) [P(3HB-co-3HV)] by fed-batch culture of Ralstoniaeutropha was optimized to achieve high cell density and high 3HV yield. Effects of different feedingstrategies of propionic acid on the production of P(3HB-co-3HV) were investigated. A decline ofspecific synthesis rate of copolymer and the yield of 3HV unit from propionic acid were observed dueto the propionic acid accumulation in culture broth when the feeding solution with highP/G(propionic acid to glucose) ratio was employed. It was further confirmed by controlling propionicacid concentration at a low level in the separate feeding of propionic acid. An optimal feedingstrategy was demonstrated to reduce the propionic acid accumulation. The cell concentration,P(3HB-co-3HV) productivity and 3HV unit fraction reached to 163.9kg·m^(-3), 1.8kg·m^(-3)·h^(-1),and 10.6%(by mass), respectively, resulting in a yield of 0.33g HV per g propionic acid.展开更多
Feeding activities provide necessary nutrition and energy to support the reproduction and development of fish populations.The feeding ecology and dietary plasticity of fish are important factors determining their recr...Feeding activities provide necessary nutrition and energy to support the reproduction and development of fish populations.The feeding ecology and dietary plasticity of fish are important factors determining their recruitment and population dynamics.As a top predator,Japanese Spanish mackerel(Scomberomorus niphonius)supports one of the most valuable fisheries in China.In this study,the feeding ecology and diet composition of Japanese Spanish mackerel spawning groups were analysed based on samples collected from six spawning grounds along the eastern coastal waters of China during spring(March to May)in 2016 and 2017.Both stomach contents and stable isotope analysis were conducted.Stomach content analysis showed that spawning groups of Japanese Spanish mackerel mainly fed on fish,consuming more than 40 different prey species.Diets were significantly different among sampling locations.The most important prey species were Stolephorus in Fuzhou,Japanese anchovy Engraulis japonicus in Xiangshan,Euphausia pacifica in Lüsi,sand lance Ammodytes personatus in Qingdao and Weihai,and Leptochela gracilis in Laizhou Bay.Stable isotope analysis showed that the trophic level of Japanese Spanish mackerel was relatively high and generally increased with latitude from south to north.In the 1980 s,the diet of Japanese Spanish mackerel was dominated solely by Japanese anchovies in the eastern coastal waters of China.The results in the present study showed that the importance of Japanese anchovies declined considerably,and this fish was not the most dominant diet in most of the investigated waters.Both the spatial variations in diet composition and changes in the dominant diet over the long term indicated the high adaptability of Japanese Spanish mackerel to the environment.Combining the results of stomach analysis and stable isotope analysis from different tissues provided more comprehensive and accurate dietary information on Japanese Spanish mackerel.The study provides essential information about the feeding ecology of Japanese Spanish mackerel and will benefit the management of its populations in the future.展开更多
The combined effects of feeding rate(0.8%,1.0%,and 1.2%initial body weight/day),feeding frequency(two,three,and four times/day) and stocking density(10,15,and 20 kg/m3) in recirculating aquaculture systems(RAS) on gro...The combined effects of feeding rate(0.8%,1.0%,and 1.2%initial body weight/day),feeding frequency(two,three,and four times/day) and stocking density(10,15,and 20 kg/m3) in recirculating aquaculture systems(RAS) on growth performance,digestion and waste generation of Atlantic salmon(Salmo salar L.) were investigated in an 8-week orthogonal experiment(L9(3)3) with a constant daily water renewal at 7.50%of total volume.No mortality occurred during the experimental period.Feed conversion ratio(FCR) varied from 0.90 to 1.13 and specific growth rate(SGR) ranged from 0.48%to 0.69%/day.SGR,thermal growth coefficient(TGC) and FCR were not significantly(P>0.05) affected by the three factors,while net protein utilization(NPU) was significantly(P<0.05) affected.Apparent digestibility coefficients(ADC) of dry matter in the present study were in the range 66.12%-73.55%.ADC in protein,lipid and energy were statistically different among all treatments and in the range of 90.07%-93.67%,81.54%-89.15%,and67.55%-71.87%,respectively.The proportion of mean total ammonia nitrogen excreted ranged from 1.37%to 1.64%of feed nitrogen at steady state,and the concentration of nitrogenous and phosphorus compounds were differently correlated to the three factors.The results will provide valuable reference data for culture management decisions in the Atlantic salmon farming industry.展开更多
The design and analysis of continuum robots have consistently been a prominent research focus in the field of mechanics.However,portable continuum robots with minimal spatial occupancy,which have great potential for a...The design and analysis of continuum robots have consistently been a prominent research focus in the field of mechanics.However,portable continuum robots with minimal spatial occupancy,which have great potential for applications such as search and rescue,are scarcely available.This paper presents a novel helical-coiled multi-segment flexible continuum robot featuring helical deployment and compact design,with an integrated framework for structural design,kinematic modeling,and experimental validation.The design of the helical-coiled multi-segment flexible continuum robot for unstructured environment detection,including a flexible body,an actuation module,a feed module,and a sensing module,is presented systematically.Kinematic models of both single-and multisegment continuum robots were established based on the constant curvature model to analyze the parameter mapping relationship from the end-effector position and orientation to the driving inputs.Furthermore,the feedforward motion of the robot was examined,and an uncoiling strategy based on S-curve compensation was employed to complete the kinematic analysis.Finally,the accuracy of the kinematic model considering the active uncoiling feed motion was validated through experimental analysis,demonstrating the motion characteristics of the continuum robot.Altogether,this study provides a framework for the design and analysis of helical-coiled continuum robots.展开更多
Optimal glucose feed strategy for glycerol fed-batch fermentation was investigated by Pontryagin’s maximum principle to maximize the final glycerol yield. The problem was solved by a nonsingular control approach by s...Optimal glucose feed strategy for glycerol fed-batch fermentation was investigated by Pontryagin’s maximum principle to maximize the final glycerol yield. The problem was solved by a nonsingular control approach by selecting the culture volume as the control variable, then the general optimal feed profile was numerically determined.展开更多
(R)-2-Hydroxy-4-phenylbutyric acid ethyl ester((R)-HPBE)is an essential chiral intermediate in the synthesis of angiotensin-converting enzyme(ACE)inhibitors.Its production involves the highly selective asymmetric redu...(R)-2-Hydroxy-4-phenylbutyric acid ethyl ester((R)-HPBE)is an essential chiral intermediate in the synthesis of angiotensin-converting enzyme(ACE)inhibitors.Its production involves the highly selective asymmetric reduction of ethyl 2-oxo-4-phenylbutyrate(OPBE),catalyzed by carbonyl reductase(CpCR),with efficient cofactor regeneration playing a crucial role.In this study,an in-situ coenzyme regeneration system was developed by coupling carbonyl reductase(CpCR)with glucose dehydrogenase(GDH),resulting in the construction of five recombinant strains capable of NADPH regeneration.Among these,the recombinant strain E.coli BL21-pETDuet-1-GDH-L-CpCR,where CpCR is fused to the C-terminus of GDH,demonstrated the highest catalytic activity.This strain exhibited an enzyme activity of 69.78 U/mg and achieved a conversion rate of 98.3%,with an enantiomeric excess(ee)of 99.9%during the conversion of 30 mM OPBE to(R)-HPBE.High-density fermentation further enhanced enzyme yield,achieving an enzyme activity of 1960 U/mL in the fermentation broth,which is 16.2 times higher than the volumetric activity obtained from shake flask fermentation.Additionally,the implementation of a substrate feeding strategy enabled continuous processing,allowing the strain to efficiently convert a final OPBE concentration of 920 mM,producing 912 mM of(R)-HPBE.These findings highlight the system’s improved catalytic efficiency,stability,and scalability,making it highly suitable for industrial-scale biocatalytic production.展开更多
Single-species management ignores the interactions between species,and ecosystem-based fisheries management(EBFM)has become a main method to fisheries management.Understanding food web structures and species interacti...Single-species management ignores the interactions between species,and ecosystem-based fisheries management(EBFM)has become a main method to fisheries management.Understanding food web structures and species interactions is essential for the implementation of EBFM and maintenance of ecosystem functions.Overfishing is one of the main reasons behind the depletion,which could even lead to the depletion of some target species in local areas.So understanding the impacts of species depletion on food web structures is important for the implementation of EBFM.The impacts of species depletion can be transmitted through the food web and cause the local extinction of both target and non-target species.In this study,topological network analysis was applied to examine the impacts of species depletion on the food web structure of Haizhou Bay.Results showed that fine crayfish Leptochela gracilis,squid Loligo sp.,and Japanese snapping shrimp Alpheus japonicus have the highest numbers of outgoing links(48,32 and 31 respectively);thus,these species may be considered key prey species.Whitespotted conger Conger myriaster,fat greenling Hexagrammos otakii,and bluefin gurnard Chelidonichthys kumu were key predators with the highest number of incoming links(37,36 and 35 respectively).The competition graphs derived from the Haizhou Bay food web were highly connected(more than 40%predators sharing over 10 common prey species),and showed close trophic interaction between high trophic level fishes.Simulation analysis showed that the food web structure has small changes to the depletion of species in a highly complex food web.The most-connected target species did not necessarily indicate high structural importance;however,some species with low connectivity may demonstrate stronger trophic interactions and play important ecological roles in the food web.But most species were more sensitive to the depletion of the most-connected target species than other target species(for instance,for zooplankton,closeness centrality 13.876 in D6,but closeness centrality 82.143 in original food web).Therefore,EBFM should focus on the most-connected target species,but also on those species with few but strong links and feeding relationships in the food web.展开更多
Background:Erythromycin production often has concern with the consumption rate of amino nitrogen and phosphate,especially in the early fermentation phase.The dynamic regulation of nitrogen and phosphorus was put forwa...Background:Erythromycin production often has concern with the consumption rate of amino nitrogen and phosphate,especially in the early fermentation phase.The dynamic regulation of nitrogen and phosphorus was put forward based on the comprehensive analysis of the contents of phosphorus and nitrogen in different nitrogen sources as well as the relations between nitrogen consumption and phosphorus consumption.Results:Firstly,the unstable nitrogen source,corn steep liquor,was substituted with the stable nitrogen source,yeast powder,with little effects on erythromycin production.Secondly,feeding phosphate in the early fermentation stage accelerated the consumption of amino nitrogen and ultimately increased erythromycin production by approximately 24%as compared with the control(without feeding potassium dihydrogen phosphate).Thirdly,feeding phosphate strategy successfully applied to 500 L fermenter with the final erythromycin concentration of 11839 U/mL,which was 17.3%higher than that of the control.Finally,the application of condensed soy protein(a cheap nitrogen source with low phosphorus content)combined with phosphate feed strategy led to a 13.0%increase of the erythromycin production as compared with the control(condensed soy protein,without feeding potassium dihydrogen phosphate).Conclusions:Appropriately feeding phosphate combined with rational nitrogen regulation in the early fermentation phase was an effective way to improve erythromycin production.展开更多
Euphausia superba and Thysanoessa macrura are dominant krill species in the Southern Ocean and their habitats are often overlapped reportedly.Studies of the feeding strategies of these two krill species will help us b...Euphausia superba and Thysanoessa macrura are dominant krill species in the Southern Ocean and their habitats are often overlapped reportedly.Studies of the feeding strategies of these two krill species will help us better understand the coexistence mechanisms and estimate the roles that krill played in the food web of the Southern Ocean.The trophodynamics of E.superba and T.macrura at different ontogenetic stages(furcilia,juvenile,adult)were studied using fatty acid and stable isotope biomarkers in the samples collected in Amundsen Sea during austral summer of 2017/2018 and 2018/2019.Diatoms like Fragilariopsis spp.was the most abundant phytoplankton species in the summer of 2017/2018,while the abundance of phytoplankton in the summer of 2018/2019 was dominated by Phaeocystis sp.The gradual increase of the carnivorous index 18꞉1n-9/18꞉1n-7 with ontogeny of both species in 2018/2019 indicated more carnivorous feeding of adults compared with juveniles and larvae.Meanwhile,greaterδ15N values of T.macrura than that of E.superba were more significant in the juvenile and adult stages during the summer of 2018/2019.Our results indicate that the trophic niche differentiation between the two krill species appeared in postlarval stage and can be influenced by food availability.Compared with E.superba,T.macrura was more prone to feed omnivorously or carnivorously responding to food availability.展开更多
The aquaculture sector provides the primary protein source for the global population while generating income and revenue(FAO,2020).Apart from that,aquaculturists are responsible for developing and maintaining sustaina...The aquaculture sector provides the primary protein source for the global population while generating income and revenue(FAO,2020).Apart from that,aquaculturists are responsible for developing and maintaining sustainable production methods,including aquafeed production(Albrektsen et al.,2022).展开更多
This study investigated the effect of hazelnut skin by-products supplementation on lamb myofibrillar proteome changes during post-mortem storage(0,4,and 7 days).Gel-based proteomics and bioinformatics approaches were ...This study investigated the effect of hazelnut skin by-products supplementation on lamb myofibrillar proteome changes during post-mortem storage(0,4,and 7 days).Gel-based proteomics and bioinformatics approaches were applied to reveal the underlying biochemical pathways and their importance in lamb meat texture development.Twenty-two Valle del Belice male lambs were randomly assigned to two dietary treatments:control(C)for lambs fed with maize-barley diet,and hazelnut skin(H)for lambs fed hazelnut skin by-product as maize partial replacer in the concentrate diet(150 g/kg DM basis).A greater myofibrillar fragmentation index(MFI)was found in meat from the C group at day 0 of storage(91.33 vs 98.38 in H and C groups,respectively).Conversely,starting from 4 days of storage,higher MFI values were observed in meat from lambs fed hazelnut skin(113.74 and 116.1 vs 99.28 and 107.26 in H and C groups at 4 and 7 days,respectively).Myofibrillar proteome changes estimated by SDS-PAGE and immunoblotting revealed a degradation of desmin(P<0.01)and troponin T(P<0.001)intact proteins,and an increase in the abundance of the appearing 30 kDa fragment(P<0.001)after 4 days of storage in meat from H than the C group.In-depth proteomics and bioinformatics revealed 44 proteoforms(26 unique proteins),mainly involved in actin filament-based process/cytoskeleton organization,energy metabolism,and heat shock proteins,as the major interconnected pathways impacted by hazelnut by-product feeding strategy on lamb meat quality.Twelve proteins were proposed in this trial as po-tential biomarkers of lamb meat texture as a consequence of hazelnut skin by-products supplementation.展开更多
基金The Public Science and Technology Research Funds Projects of Ocean under contract No.201505026the Fujian Province Natural Science Foundation under contract Nos 2016J01160 and 2017N0015the Scientific Research Foundation of Third Institute of Oceanography,SOA under contract No.2016038
文摘Agarases are hydrolytic enzymes that act on the hydrolysis of agar and have a broad range of applications in food,cosmetics and pharmaceutical industries. In this study, a glycerol feeding strategy based on induction mode optimization for high cell density and β-agarase production was established, which could effectively control acetate yield. First, exponential feeding strategy of glycerol with different overall specific growth rates（μ） was applied in the pre-induction phase. The results showed that the low μ（μ=0.2） was suggested to be the optimal for cell growth and β-agarase production. Second, the effects of induction temperature and the inducer concentration on cell growth and β-agarase production were investigated in the post-induction phase. When induced by isopropyl-β-d-thiogalactoside（IPTG）, the strategy of 0.8 mmol/L IPTG induction at 20℃ was found to be optimal for β-agarase production. When cultivation was induced by continuous lactose feeding strategy of 1.0 g/（L·h）, the β-agarase activity reached 112.5 U/mL, which represented the highest β-agarase production to date.Furthermore, the β-agarase was capable of degrading G. lemaneiformis powder directly to produce neoagarooligosaccharide, and the hydrolysates were neoagarotetraose（NA4） and neoagarohexaose（NA6）. The overall research may be useful for the industrial production and application of β-agarase.
文摘This study was conducted to valorize four sources of fiber (Gliricidia sepium, Leucaena leucocephala, Moringa oleifera and palm nut fibers) in animal production. The experiments were carried out on 128 rabbits divided into 4 batches of 32 animals, reared for 8 weeks under the same conditions. Each batch was subdivided into two subgroups, one fed with a complete diet (a diet containing one of the fiber sources and served all day) and the other with the same diet separated from the fiber source (served at 9 a.m. and supplemented with the fiber source at 4 p.m.). Eight (8) experimental rations were, respectively, tested on the subgroups: complete feed Gliricidia sepium (CFG);supplemented feed Gliricidia sepium (SFG);complete feed Leucaena leucocephala (CFL);supplemented feed Leucaena leucocephala (SFL);complete feed Moringa oleifera (CFM);supplemented feed Moringa oleifera (SFM);complete feed palm nut fiber (CFF);supplemented feed palm nut fiber (SFF). In each subgroup, 4 rabbits were slaughtered at 15 weeks of age for a total of 32 rabbits. Physico-chemical parameters were evaluated on the feed and the meat. Data were analyzed using SAS 2013 software. Fiber content was similar (p > 0.05) for complete feeds. Fat content was high (p < 0.001) for the palm nuts fiber (27.34%) and the CFF feed (11.36%). Feeding rabbits with G. sepium leaves or palm nut fiber continuously increased the fat content of the meat in contrast to sequential feeding. Meat quality was also better when the fiber source was used in the feed of the rabbits in the evening.
文摘The feeding method of propionic acid for production ofpoly(3-hydroxybutyrate-co-3-hydro xyvalerate) [P(3HB-co-3HV)] by fed-batch culture of Ralstoniaeutropha was optimized to achieve high cell density and high 3HV yield. Effects of different feedingstrategies of propionic acid on the production of P(3HB-co-3HV) were investigated. A decline ofspecific synthesis rate of copolymer and the yield of 3HV unit from propionic acid were observed dueto the propionic acid accumulation in culture broth when the feeding solution with highP/G(propionic acid to glucose) ratio was employed. It was further confirmed by controlling propionicacid concentration at a low level in the separate feeding of propionic acid. An optimal feedingstrategy was demonstrated to reduce the propionic acid accumulation. The cell concentration,P(3HB-co-3HV) productivity and 3HV unit fraction reached to 163.9kg·m^(-3), 1.8kg·m^(-3)·h^(-1),and 10.6%(by mass), respectively, resulting in a yield of 0.33g HV per g propionic acid.
基金The Marine S&T Fund of Shandong Province for Pilot National Laboratory for Marine Science and Technology(Qingdao)under contract No.2018SDKJ0501-2the National Key R&D Program of China under contract No.2017YEE0104400the National Natural Science Foundation of China under contract Nos 31772852 and 31802301。
文摘Feeding activities provide necessary nutrition and energy to support the reproduction and development of fish populations.The feeding ecology and dietary plasticity of fish are important factors determining their recruitment and population dynamics.As a top predator,Japanese Spanish mackerel(Scomberomorus niphonius)supports one of the most valuable fisheries in China.In this study,the feeding ecology and diet composition of Japanese Spanish mackerel spawning groups were analysed based on samples collected from six spawning grounds along the eastern coastal waters of China during spring(March to May)in 2016 and 2017.Both stomach contents and stable isotope analysis were conducted.Stomach content analysis showed that spawning groups of Japanese Spanish mackerel mainly fed on fish,consuming more than 40 different prey species.Diets were significantly different among sampling locations.The most important prey species were Stolephorus in Fuzhou,Japanese anchovy Engraulis japonicus in Xiangshan,Euphausia pacifica in Lüsi,sand lance Ammodytes personatus in Qingdao and Weihai,and Leptochela gracilis in Laizhou Bay.Stable isotope analysis showed that the trophic level of Japanese Spanish mackerel was relatively high and generally increased with latitude from south to north.In the 1980 s,the diet of Japanese Spanish mackerel was dominated solely by Japanese anchovies in the eastern coastal waters of China.The results in the present study showed that the importance of Japanese anchovies declined considerably,and this fish was not the most dominant diet in most of the investigated waters.Both the spatial variations in diet composition and changes in the dominant diet over the long term indicated the high adaptability of Japanese Spanish mackerel to the environment.Combining the results of stomach analysis and stable isotope analysis from different tissues provided more comprehensive and accurate dietary information on Japanese Spanish mackerel.The study provides essential information about the feeding ecology of Japanese Spanish mackerel and will benefit the management of its populations in the future.
基金Supported by the Modern Agro-Industry Technology Research System(No.CARS-48)the National Natural Science Foundation of China(No.31240012)+1 种基金the Special Foundation for Postdoctoral Innovative Projects of Shandong Province(No.201101009)the National Key Technology R&D Program of China(No.2011BAD13B04)
文摘The combined effects of feeding rate(0.8%,1.0%,and 1.2%initial body weight/day),feeding frequency(two,three,and four times/day) and stocking density(10,15,and 20 kg/m3) in recirculating aquaculture systems(RAS) on growth performance,digestion and waste generation of Atlantic salmon(Salmo salar L.) were investigated in an 8-week orthogonal experiment(L9(3)3) with a constant daily water renewal at 7.50%of total volume.No mortality occurred during the experimental period.Feed conversion ratio(FCR) varied from 0.90 to 1.13 and specific growth rate(SGR) ranged from 0.48%to 0.69%/day.SGR,thermal growth coefficient(TGC) and FCR were not significantly(P>0.05) affected by the three factors,while net protein utilization(NPU) was significantly(P<0.05) affected.Apparent digestibility coefficients(ADC) of dry matter in the present study were in the range 66.12%-73.55%.ADC in protein,lipid and energy were statistically different among all treatments and in the range of 90.07%-93.67%,81.54%-89.15%,and67.55%-71.87%,respectively.The proportion of mean total ammonia nitrogen excreted ranged from 1.37%to 1.64%of feed nitrogen at steady state,and the concentration of nitrogenous and phosphorus compounds were differently correlated to the three factors.The results will provide valuable reference data for culture management decisions in the Atlantic salmon farming industry.
基金Supported by National Natural Science Foundation of China(Grant Nos.52305003,52175019)National Key R&D Program of China(Grant No.2023YFD2001100)+2 种基金Beijing Natural Science Foundation(Grant No.L222038)Beijing Nova Programme Interdisciplinary Cooperation Project(Grant No.20240484699)Project“Vice President of Science and Technology”of Changping District of Beijing.
文摘The design and analysis of continuum robots have consistently been a prominent research focus in the field of mechanics.However,portable continuum robots with minimal spatial occupancy,which have great potential for applications such as search and rescue,are scarcely available.This paper presents a novel helical-coiled multi-segment flexible continuum robot featuring helical deployment and compact design,with an integrated framework for structural design,kinematic modeling,and experimental validation.The design of the helical-coiled multi-segment flexible continuum robot for unstructured environment detection,including a flexible body,an actuation module,a feed module,and a sensing module,is presented systematically.Kinematic models of both single-and multisegment continuum robots were established based on the constant curvature model to analyze the parameter mapping relationship from the end-effector position and orientation to the driving inputs.Furthermore,the feedforward motion of the robot was examined,and an uncoiling strategy based on S-curve compensation was employed to complete the kinematic analysis.Finally,the accuracy of the kinematic model considering the active uncoiling feed motion was validated through experimental analysis,demonstrating the motion characteristics of the continuum robot.Altogether,this study provides a framework for the design and analysis of helical-coiled continuum robots.
基金From National Ninth Five Years Project (NO. 96-03-03-03A).
文摘Optimal glucose feed strategy for glycerol fed-batch fermentation was investigated by Pontryagin’s maximum principle to maximize the final glycerol yield. The problem was solved by a nonsingular control approach by selecting the culture volume as the control variable, then the general optimal feed profile was numerically determined.
基金supported by the Zhejiang Provincial Science and Technology Plan Project(2024C03014)the National Nature Science Foundation of China(Project Nos.21978267,and 22078300)as well as the Natural Science Foundation of Heilongjiang Province(LH2022H107).
文摘(R)-2-Hydroxy-4-phenylbutyric acid ethyl ester((R)-HPBE)is an essential chiral intermediate in the synthesis of angiotensin-converting enzyme(ACE)inhibitors.Its production involves the highly selective asymmetric reduction of ethyl 2-oxo-4-phenylbutyrate(OPBE),catalyzed by carbonyl reductase(CpCR),with efficient cofactor regeneration playing a crucial role.In this study,an in-situ coenzyme regeneration system was developed by coupling carbonyl reductase(CpCR)with glucose dehydrogenase(GDH),resulting in the construction of five recombinant strains capable of NADPH regeneration.Among these,the recombinant strain E.coli BL21-pETDuet-1-GDH-L-CpCR,where CpCR is fused to the C-terminus of GDH,demonstrated the highest catalytic activity.This strain exhibited an enzyme activity of 69.78 U/mg and achieved a conversion rate of 98.3%,with an enantiomeric excess(ee)of 99.9%during the conversion of 30 mM OPBE to(R)-HPBE.High-density fermentation further enhanced enzyme yield,achieving an enzyme activity of 1960 U/mL in the fermentation broth,which is 16.2 times higher than the volumetric activity obtained from shake flask fermentation.Additionally,the implementation of a substrate feeding strategy enabled continuous processing,allowing the strain to efficiently convert a final OPBE concentration of 920 mM,producing 912 mM of(R)-HPBE.These findings highlight the system’s improved catalytic efficiency,stability,and scalability,making it highly suitable for industrial-scale biocatalytic production.
基金The National Key R&D Program of China under contract No.2018YFD0900904the National Natural Science Foundation of China under contract Nos 31772852 and 31802301。
文摘Single-species management ignores the interactions between species,and ecosystem-based fisheries management(EBFM)has become a main method to fisheries management.Understanding food web structures and species interactions is essential for the implementation of EBFM and maintenance of ecosystem functions.Overfishing is one of the main reasons behind the depletion,which could even lead to the depletion of some target species in local areas.So understanding the impacts of species depletion on food web structures is important for the implementation of EBFM.The impacts of species depletion can be transmitted through the food web and cause the local extinction of both target and non-target species.In this study,topological network analysis was applied to examine the impacts of species depletion on the food web structure of Haizhou Bay.Results showed that fine crayfish Leptochela gracilis,squid Loligo sp.,and Japanese snapping shrimp Alpheus japonicus have the highest numbers of outgoing links(48,32 and 31 respectively);thus,these species may be considered key prey species.Whitespotted conger Conger myriaster,fat greenling Hexagrammos otakii,and bluefin gurnard Chelidonichthys kumu were key predators with the highest number of incoming links(37,36 and 35 respectively).The competition graphs derived from the Haizhou Bay food web were highly connected(more than 40%predators sharing over 10 common prey species),and showed close trophic interaction between high trophic level fishes.Simulation analysis showed that the food web structure has small changes to the depletion of species in a highly complex food web.The most-connected target species did not necessarily indicate high structural importance;however,some species with low connectivity may demonstrate stronger trophic interactions and play important ecological roles in the food web.But most species were more sensitive to the depletion of the most-connected target species than other target species(for instance,for zooplankton,closeness centrality 13.876 in D6,but closeness centrality 82.143 in original food web).Therefore,EBFM should focus on the most-connected target species,but also on those species with few but strong links and feeding relationships in the food web.
基金financially supported by a grant from the Major State Basic Research Development Program of China(973 Program,No.2012CB721006)National Natural Science Foundation of China(No.21276081)+1 种基金National Scientific and Technological Major Special Project(Significant Creation of New drugs,No.2011ZX09203-001-03)Research Fund for the Doctoral Program of Higher Education of China(No.20110074110015).
文摘Background:Erythromycin production often has concern with the consumption rate of amino nitrogen and phosphate,especially in the early fermentation phase.The dynamic regulation of nitrogen and phosphorus was put forward based on the comprehensive analysis of the contents of phosphorus and nitrogen in different nitrogen sources as well as the relations between nitrogen consumption and phosphorus consumption.Results:Firstly,the unstable nitrogen source,corn steep liquor,was substituted with the stable nitrogen source,yeast powder,with little effects on erythromycin production.Secondly,feeding phosphate in the early fermentation stage accelerated the consumption of amino nitrogen and ultimately increased erythromycin production by approximately 24%as compared with the control(without feeding potassium dihydrogen phosphate).Thirdly,feeding phosphate strategy successfully applied to 500 L fermenter with the final erythromycin concentration of 11839 U/mL,which was 17.3%higher than that of the control.Finally,the application of condensed soy protein(a cheap nitrogen source with low phosphorus content)combined with phosphate feed strategy led to a 13.0%increase of the erythromycin production as compared with the control(condensed soy protein,without feeding potassium dihydrogen phosphate).Conclusions:Appropriately feeding phosphate combined with rational nitrogen regulation in the early fermentation phase was an effective way to improve erythromycin production.
基金Supported by the National Key Research and Development Plan of China(No.2018YFC1406801)the National Natural Science Foundation of China(No.41876217)+1 种基金the Impact and Response of Antarctic Seas to Climate Change(No.IRASCC 01-02-01D)the Taishan Scholars Program。
文摘Euphausia superba and Thysanoessa macrura are dominant krill species in the Southern Ocean and their habitats are often overlapped reportedly.Studies of the feeding strategies of these two krill species will help us better understand the coexistence mechanisms and estimate the roles that krill played in the food web of the Southern Ocean.The trophodynamics of E.superba and T.macrura at different ontogenetic stages(furcilia,juvenile,adult)were studied using fatty acid and stable isotope biomarkers in the samples collected in Amundsen Sea during austral summer of 2017/2018 and 2018/2019.Diatoms like Fragilariopsis spp.was the most abundant phytoplankton species in the summer of 2017/2018,while the abundance of phytoplankton in the summer of 2018/2019 was dominated by Phaeocystis sp.The gradual increase of the carnivorous index 18꞉1n-9/18꞉1n-7 with ontogeny of both species in 2018/2019 indicated more carnivorous feeding of adults compared with juveniles and larvae.Meanwhile,greaterδ15N values of T.macrura than that of E.superba were more significant in the juvenile and adult stages during the summer of 2018/2019.Our results indicate that the trophic niche differentiation between the two krill species appeared in postlarval stage and can be influenced by food availability.Compared with E.superba,T.macrura was more prone to feed omnivorously or carnivorously responding to food availability.
文摘The aquaculture sector provides the primary protein source for the global population while generating income and revenue(FAO,2020).Apart from that,aquaculturists are responsible for developing and maintaining sustainable production methods,including aquafeed production(Albrektsen et al.,2022).
文摘This study investigated the effect of hazelnut skin by-products supplementation on lamb myofibrillar proteome changes during post-mortem storage(0,4,and 7 days).Gel-based proteomics and bioinformatics approaches were applied to reveal the underlying biochemical pathways and their importance in lamb meat texture development.Twenty-two Valle del Belice male lambs were randomly assigned to two dietary treatments:control(C)for lambs fed with maize-barley diet,and hazelnut skin(H)for lambs fed hazelnut skin by-product as maize partial replacer in the concentrate diet(150 g/kg DM basis).A greater myofibrillar fragmentation index(MFI)was found in meat from the C group at day 0 of storage(91.33 vs 98.38 in H and C groups,respectively).Conversely,starting from 4 days of storage,higher MFI values were observed in meat from lambs fed hazelnut skin(113.74 and 116.1 vs 99.28 and 107.26 in H and C groups at 4 and 7 days,respectively).Myofibrillar proteome changes estimated by SDS-PAGE and immunoblotting revealed a degradation of desmin(P<0.01)and troponin T(P<0.001)intact proteins,and an increase in the abundance of the appearing 30 kDa fragment(P<0.001)after 4 days of storage in meat from H than the C group.In-depth proteomics and bioinformatics revealed 44 proteoforms(26 unique proteins),mainly involved in actin filament-based process/cytoskeleton organization,energy metabolism,and heat shock proteins,as the major interconnected pathways impacted by hazelnut by-product feeding strategy on lamb meat quality.Twelve proteins were proposed in this trial as po-tential biomarkers of lamb meat texture as a consequence of hazelnut skin by-products supplementation.
