As a soluble food raw material with a low calorie content,resistant dextrin (RD) has broad application prospects in the food industry.Branching enzymes (BEs),as a key enzyme for RD preparation,can break the α-1,4 gly...As a soluble food raw material with a low calorie content,resistant dextrin (RD) has broad application prospects in the food industry.Branching enzymes (BEs),as a key enzyme for RD preparation,can break the α-1,4 glycosidic bonds of donor chains and reconstruct the cleaved chains to acceptor chains through the α-1,6 glycosidic bonds.BEs with high transglucosidic activity toward amylopectin and short-chain substrates are urgently needed to increase the quality of RD.Herein,BE derived from Thermuobifida fusca (TfBE) was mined and characterized.The optimal temperature and pH of the TfBE were 40 ℃ and 6.5,respectively.A total of 1500 U/g substrate TfBE reacted with 20% (w/v) pyrodextrin for 12 h,the ratio of α-1,4 to α-1,6 glycosidic bonds was changed from 3.52:1 to 2.33:1,and the content of enzyme-resistant components notably increased from 44.0% to 53.8%.Furthermore,to make full use of receptor chains and small molecular sugars in the reaction system,a multienzyme complex of TfBE with T.fusca α-cyclodextrin glucosyltransferase (TfCGTase),TfBE with TfCGTase and Aspergillus nidulans α-glucosidase (AnGS) was used to further increase the enzyme resistance of RD from 44.0% to 65.3% and 70.6%,respectively.The developed multienzyme complex method could effectively contribute to improving the production quality and efficiency of RD preparation.展开更多
Nicotiana tabacum is one of the representative high-value crops with distinctive aromatic flavors,holding sig-nificant economic importance and research value worldwide.Carotenoid cleavage products are known to be majo...Nicotiana tabacum is one of the representative high-value crops with distinctive aromatic flavors,holding sig-nificant economic importance and research value worldwide.Carotenoid cleavage products are known to be major contributors to plant flavor,but their expression patterns and underlying mechanisms in N.tabacum remain ambiguous.In this study,21 carotenoid cleavage dioxygenase(CCD)family members were identified in Nicotiana tabacum through genomic analysis and 3 novel members from the CCD1,CCD4,and CCD7 subfamilies were heterologously expressed.Functional assays revealed remarkable thermal tolerance,with NtCCD4 exhib-iting an optimal activity temperature of 50℃.All enzymes efficiently catalyzedβ-carotene cleavage,producingβ-ionone,β-cyclocitral,and other related compounds.Cleavage sites were inferred through targeted site muta-tions.By combining three enzymes in several complex preparations,distinct substrate conversion patterns emerged,with different enzymes dominating and altering the quantity and composition of aroma compounds.In post-roasted tobacco and tea leaves,treatment with a multienzyme system increased total aroma intensity(~2.5-5-fold),boosting sweet and roasted aromas in tobacco and grassy and floral notes in tea.This study re-ported the catalytic patterns of enzymes from three CCD subfamilies,and confirmed their positive contribution to enhancing plant aroma quality.They also paved the way for exogenous regulation of flavor synthesis.展开更多
基金financial support from the National Natural Science Foundation of China(31972032)the National Natural Science Foundation of China(31730067)+1 种基金the Independent Innovation Project of Jiangsu Province(CX(21)3039)the Science Foundation of Jiangsu Province(BK20190586).
文摘As a soluble food raw material with a low calorie content,resistant dextrin (RD) has broad application prospects in the food industry.Branching enzymes (BEs),as a key enzyme for RD preparation,can break the α-1,4 glycosidic bonds of donor chains and reconstruct the cleaved chains to acceptor chains through the α-1,6 glycosidic bonds.BEs with high transglucosidic activity toward amylopectin and short-chain substrates are urgently needed to increase the quality of RD.Herein,BE derived from Thermuobifida fusca (TfBE) was mined and characterized.The optimal temperature and pH of the TfBE were 40 ℃ and 6.5,respectively.A total of 1500 U/g substrate TfBE reacted with 20% (w/v) pyrodextrin for 12 h,the ratio of α-1,4 to α-1,6 glycosidic bonds was changed from 3.52:1 to 2.33:1,and the content of enzyme-resistant components notably increased from 44.0% to 53.8%.Furthermore,to make full use of receptor chains and small molecular sugars in the reaction system,a multienzyme complex of TfBE with T.fusca α-cyclodextrin glucosyltransferase (TfCGTase),TfBE with TfCGTase and Aspergillus nidulans α-glucosidase (AnGS) was used to further increase the enzyme resistance of RD from 44.0% to 65.3% and 70.6%,respectively.The developed multienzyme complex method could effectively contribute to improving the production quality and efficiency of RD preparation.
基金supported by the Key Science and Technology Program of Hunan Provincial Tobacco Corporation(HN2023KJ04,HN2024KJ01,HN2025KJ01)support provided by the China Postdoctoral Science Foundation Program(2025T015HN,2025M782868).
文摘Nicotiana tabacum is one of the representative high-value crops with distinctive aromatic flavors,holding sig-nificant economic importance and research value worldwide.Carotenoid cleavage products are known to be major contributors to plant flavor,but their expression patterns and underlying mechanisms in N.tabacum remain ambiguous.In this study,21 carotenoid cleavage dioxygenase(CCD)family members were identified in Nicotiana tabacum through genomic analysis and 3 novel members from the CCD1,CCD4,and CCD7 subfamilies were heterologously expressed.Functional assays revealed remarkable thermal tolerance,with NtCCD4 exhib-iting an optimal activity temperature of 50℃.All enzymes efficiently catalyzedβ-carotene cleavage,producingβ-ionone,β-cyclocitral,and other related compounds.Cleavage sites were inferred through targeted site muta-tions.By combining three enzymes in several complex preparations,distinct substrate conversion patterns emerged,with different enzymes dominating and altering the quantity and composition of aroma compounds.In post-roasted tobacco and tea leaves,treatment with a multienzyme system increased total aroma intensity(~2.5-5-fold),boosting sweet and roasted aromas in tobacco and grassy and floral notes in tea.This study re-ported the catalytic patterns of enzymes from three CCD subfamilies,and confirmed their positive contribution to enhancing plant aroma quality.They also paved the way for exogenous regulation of flavor synthesis.
