Fungal iterative type I polyketide synthases(iPKSs)are commonly classified into nonreducing(NR-),partially reducing(PR-),and highly reducing(HR-)polyketide synthases based on their assembly mechanisms and domain struc...Fungal iterative type I polyketide synthases(iPKSs)are commonly classified into nonreducing(NR-),partially reducing(PR-),and highly reducing(HR-)polyketide synthases based on their assembly mechanisms and domain structures.These iPKSs have been considered functionally and evolutionarily distinct,characterized by clear boundaries.However,emerging genomic analyses suggest that the diversity of iPKSs in fungi is far from fully understood.Here,we describe the discovery and characterization of PbPKS1 from a marine-derived fungus Penicillium brocae HDN12-143,which exhibits an atypical domain organization arranged as KR-KS-AT-PT-ACP1-ACP2-CMeT-TE.Heterologous expression of PbPKS1 resulted in the production of two monohydroxybenzoic acids and two pyrones.In vivo and in vitro characterizations demonstrated that PbPKS1 has the capability to synthesize Cα-methylated partially reducing polyketides,yet involved a NR-PKS-like assembly mechanism,featuring a product template(PT)domain for aldol cyclization and a C-terminal thioesterase(TE)domain for product release.Phylogenetic analysis suggests that PbPKS1 belongs to a non-canonical PR-PKS(nPR-PKS)family,which is a minor grouping across the fungal kingdom,and possibly evolved from an NR-PKS through gene recombination.The discovery of nPR-PKS not only expands the diversity of iPKSs but also provides new insights into the evolutionary development of fungal iPKSs.展开更多
Maltodextrin is a significant ingredient extensively used in food industries,but its application is limited due to uneven polymerization and high reducibility.Hence,preparation of nonreducing maltodextrin with narrow ...Maltodextrin is a significant ingredient extensively used in food industries,but its application is limited due to uneven polymerization and high reducibility.Hence,preparation of nonreducing maltodextrin with narrow distribution of DP is essential.A dual-enzyme cascade enzymatic reaction for preparing nonreducing maltoheptaose(N-G7)is feasible via recombinant cyclomaltodextrinase(EC 3.2.1.54,CDase)and maltooligosyltrehalose synthase(EC 5.4.99.15,MTSase)heterologously overexpressed in Escherichia coli BL21(DE3).However,during this process,N-G7 further was hydrolyzed into small molecule maltooligosaccharides by the amylases homologously expressed in the host.In this study,twoα-amylase genes(ycjM and malS)were deleted to avoid host hydrolysis in N-G7 via CRISPR/Cas9 system.Gene deletion had a significant decrease on the yield of maltooligosaccharides of 5 and 6 glucose units.The defective strainsΔycjM andΔycjM-ΔmalS increased the yield of N-G7 by 21.94%and 25.47%,correspondingly.Marginal impact was made in cell growth and protein secretion of the host.YcjM and MalS were overexpressed inΔycjM-ΔmalS and the hydrolytic activity of YcjM was twice that of MalS.They constituted a complex multiple hydrolysis system for N-G7 with the Mal series enzymes involved in a maltose system in the host.展开更多
Hydrogen(H)spillover in nonreducible oxides such as zeolites and Al2O3 has been a highly controversial phenomenon in heterogeneous catalysis.Since industrial catalysts are predominantly prepared using these materials ...Hydrogen(H)spillover in nonreducible oxides such as zeolites and Al2O3 has been a highly controversial phenomenon in heterogeneous catalysis.Since industrial catalysts are predominantly prepared using these materials as supports,it is important to understand the mechanism and catalytic functions of H spillover on their surfaces.In the past decade,fundamental studies on zeolite-encapsulated metal catalysts have revealed that H spillover and reverse spillover can be utilized in the design of hydrogenation and dehydrogenation catalysts with improved properties.Both experimental and theoretical studies have indicated that H spillover can occur in nonreducible oxides when they possess substantial acid sites that aid the surface migration of active H.In the present review,we will discuss the possible mechanisms of H spillover in nonreducible oxides and the unique opportunities of using this phenomenon for the design of advanced hydroprocessing catalysts.展开更多
基金supported by Qingdao Marine Science and Technology Center(2022QNLM030003-1)the Fundamental Research Funds for the Central Universities(202172002,202262015)National Key R&D Program of China(2022YFC2807502).
文摘Fungal iterative type I polyketide synthases(iPKSs)are commonly classified into nonreducing(NR-),partially reducing(PR-),and highly reducing(HR-)polyketide synthases based on their assembly mechanisms and domain structures.These iPKSs have been considered functionally and evolutionarily distinct,characterized by clear boundaries.However,emerging genomic analyses suggest that the diversity of iPKSs in fungi is far from fully understood.Here,we describe the discovery and characterization of PbPKS1 from a marine-derived fungus Penicillium brocae HDN12-143,which exhibits an atypical domain organization arranged as KR-KS-AT-PT-ACP1-ACP2-CMeT-TE.Heterologous expression of PbPKS1 resulted in the production of two monohydroxybenzoic acids and two pyrones.In vivo and in vitro characterizations demonstrated that PbPKS1 has the capability to synthesize Cα-methylated partially reducing polyketides,yet involved a NR-PKS-like assembly mechanism,featuring a product template(PT)domain for aldol cyclization and a C-terminal thioesterase(TE)domain for product release.Phylogenetic analysis suggests that PbPKS1 belongs to a non-canonical PR-PKS(nPR-PKS)family,which is a minor grouping across the fungal kingdom,and possibly evolved from an NR-PKS through gene recombination.The discovery of nPR-PKS not only expands the diversity of iPKSs but also provides new insights into the evolutionary development of fungal iPKSs.
基金supported by the National Natural Science Foundation of China[grant number 31871745]Major Science and Technology Innovation Project of Shandong Province[grant number 2020CXGC010601].
文摘Maltodextrin is a significant ingredient extensively used in food industries,but its application is limited due to uneven polymerization and high reducibility.Hence,preparation of nonreducing maltodextrin with narrow distribution of DP is essential.A dual-enzyme cascade enzymatic reaction for preparing nonreducing maltoheptaose(N-G7)is feasible via recombinant cyclomaltodextrinase(EC 3.2.1.54,CDase)and maltooligosyltrehalose synthase(EC 5.4.99.15,MTSase)heterologously overexpressed in Escherichia coli BL21(DE3).However,during this process,N-G7 further was hydrolyzed into small molecule maltooligosaccharides by the amylases homologously expressed in the host.In this study,twoα-amylase genes(ycjM and malS)were deleted to avoid host hydrolysis in N-G7 via CRISPR/Cas9 system.Gene deletion had a significant decrease on the yield of maltooligosaccharides of 5 and 6 glucose units.The defective strainsΔycjM andΔycjM-ΔmalS increased the yield of N-G7 by 21.94%and 25.47%,correspondingly.Marginal impact was made in cell growth and protein secretion of the host.YcjM and MalS were overexpressed inΔycjM-ΔmalS and the hydrolytic activity of YcjM was twice that of MalS.They constituted a complex multiple hydrolysis system for N-G7 with the Mal series enzymes involved in a maltose system in the host.
基金supported by the Basic Science Research Program of the National Research Foundation of Korea(No.NRF-2020R1A2C3003694)the KAIST Cross-Generation Collaborative Lab Project.
文摘Hydrogen(H)spillover in nonreducible oxides such as zeolites and Al2O3 has been a highly controversial phenomenon in heterogeneous catalysis.Since industrial catalysts are predominantly prepared using these materials as supports,it is important to understand the mechanism and catalytic functions of H spillover on their surfaces.In the past decade,fundamental studies on zeolite-encapsulated metal catalysts have revealed that H spillover and reverse spillover can be utilized in the design of hydrogenation and dehydrogenation catalysts with improved properties.Both experimental and theoretical studies have indicated that H spillover can occur in nonreducible oxides when they possess substantial acid sites that aid the surface migration of active H.In the present review,we will discuss the possible mechanisms of H spillover in nonreducible oxides and the unique opportunities of using this phenomenon for the design of advanced hydroprocessing catalysts.
