Ethyl valerate, a green apple flavor is short-chain ester with fruity notes is widely used in food, cosmetic and pharmaceutical industries. Traditionally, flavor esters are produced by chemical method or extracted by ...Ethyl valerate, a green apple flavor is short-chain ester with fruity notes is widely used in food, cosmetic and pharmaceutical industries. Traditionally, flavor esters are produced by chemical method or extracted by natural sources. However, with the steadily growing demand for natural flavor compounds, the biosynthesis of such esters by lipase under mild conditions has been receiving much attention for producing these valuable products. In this study, enzymatic synthesis of ethyl valerate in solvent free system, was successfully optimized via response surface method （RSM） based on 5-level, 4-variable of central composite rotatable design （CCRD）. The parameters were reaction time （30-60 min）, reaction temperature （30-60 ℃）, amount of enzyme （10-25%, w/w） and shaking speed （50-150 rpm）. The optimum condition derived via RSM for the reaction was reaction time of 48 min, reaction temperature of 30 ℃, enzyme amount of 25%, （w/w） and shaking speed of 51 rpm. The actual experimental yield was 84.28 % under the optimum condition, which compared well with the maximum predicted value of 84.61%. Comparison of predicted and experimental values reveals good correspondence between them, implying that empirical models derived from RSM can be used to adequately describe the relationship between the factors and response in the synthesis of ethyl valerate.展开更多
A lipase from Sporisorium reilianum SRZ2(SRL)with 73%amino acid sequence identity to Candida antarctica lipase B(CALB)was cloned and overexpressed in Pichia pastoris.The recombinant SRL showed a preference for short-c...A lipase from Sporisorium reilianum SRZ2(SRL)with 73%amino acid sequence identity to Candida antarctica lipase B(CALB)was cloned and overexpressed in Pichia pastoris.The recombinant SRL showed a preference for short-chain p-nitrophenyl esters.It achieved maximum activity at pH 8.0 and 65°C for p-nitrophenyl hexanoate(C6)with Km and kcar/Km values of 0.14 mmol·L-1 and 1712 min 1.mmol·L-1 at 30℃,respec-tively.SRL displayed excellent thermostability and pH stability,retaining more than 79%of its initial activity after incubation at 60℃ for 72h and 75%atpH 3to 11 for 72 h.It also maintained most of its activity in the presence of inhibitors and detergents except sodium dodecyl sulfate,and it tolerated organic solvents.SRL was covalently immobilized and successfully used for ethyl hexanoate synthesis in cyclohexane or in a solvent-free system with a high conversion yield(>95%).Furthermore,high con-version yield was also achieved for the synthesis of various short-chain flavor esters when high substrate concentra-tions of2 mol.LI were applied.This study indicated that a.CALB-type lipase from S.reiliamum SRZ2 showed great potential in organic ester synthesis.展开更多
文摘Ethyl valerate, a green apple flavor is short-chain ester with fruity notes is widely used in food, cosmetic and pharmaceutical industries. Traditionally, flavor esters are produced by chemical method or extracted by natural sources. However, with the steadily growing demand for natural flavor compounds, the biosynthesis of such esters by lipase under mild conditions has been receiving much attention for producing these valuable products. In this study, enzymatic synthesis of ethyl valerate in solvent free system, was successfully optimized via response surface method （RSM） based on 5-level, 4-variable of central composite rotatable design （CCRD）. The parameters were reaction time （30-60 min）, reaction temperature （30-60 ℃）, amount of enzyme （10-25%, w/w） and shaking speed （50-150 rpm）. The optimum condition derived via RSM for the reaction was reaction time of 48 min, reaction temperature of 30 ℃, enzyme amount of 25%, （w/w） and shaking speed of 51 rpm. The actual experimental yield was 84.28 % under the optimum condition, which compared well with the maximum predicted value of 84.61%. Comparison of predicted and experimental values reveals good correspondence between them, implying that empirical models derived from RSM can be used to adequately describe the relationship between the factors and response in the synthesis of ethyl valerate.
文摘A lipase from Sporisorium reilianum SRZ2(SRL)with 73%amino acid sequence identity to Candida antarctica lipase B(CALB)was cloned and overexpressed in Pichia pastoris.The recombinant SRL showed a preference for short-chain p-nitrophenyl esters.It achieved maximum activity at pH 8.0 and 65°C for p-nitrophenyl hexanoate(C6)with Km and kcar/Km values of 0.14 mmol·L-1 and 1712 min 1.mmol·L-1 at 30℃,respec-tively.SRL displayed excellent thermostability and pH stability,retaining more than 79%of its initial activity after incubation at 60℃ for 72h and 75%atpH 3to 11 for 72 h.It also maintained most of its activity in the presence of inhibitors and detergents except sodium dodecyl sulfate,and it tolerated organic solvents.SRL was covalently immobilized and successfully used for ethyl hexanoate synthesis in cyclohexane or in a solvent-free system with a high conversion yield(>95%).Furthermore,high con-version yield was also achieved for the synthesis of various short-chain flavor esters when high substrate concentra-tions of2 mol.LI were applied.This study indicated that a.CALB-type lipase from S.reiliamum SRZ2 showed great potential in organic ester synthesis.
