The Study On Lipase-catalyzed Synthesis Of Sugar Ester In Non-aqueous Medium

Sugar esters are widely used nonionic surfactants. They are widely used in the food, cosmetic, detergent and pharmaceutical industry because of its high emulsifying capacity, nontoxicity, wide range of HLB value (1-16) and biodegradability. In addition,sugar esters have the effect of lubricating,detergency, foaming, anti-ageing, anti-crystallizing and anti-bacteria etc. Sugar esters are recommended food additives by FAO and WHO. Enzymatic synthesis has many advantages over conventional chemical synthesis of sugar esters. It is very important to carry out the study of enzymatic synthesis of sugar ester in non-aqueous phase. But it is very difficult to dissolve two substrate with different properties and protect the enzyme activity in single organic solvent.The reaction system is composed of substrate and organic solvent in this study and the complication of the experiment is simplified. Then sugar ester was obtained using microwave-assisted enzymatic method.In the last,the surfactant properties of the product which is synthesis by lipase in non-aqueous was measured. The main contents are as follows:(1) Firstly, the hydrolysis and synthesis activity of three kinds of lipases was measured and the most suitable lipase for non-aqueous system was found. It was Novozym435lipase. And then the lauroyl sucrose ester was synthesis in tert-butyl alcohol, tertiary amyl alcohol, acetone respectively. The product was analysis by TLC and FT-IR. The result showed that the product was composed of monoesters and diester. The FTIR showed that a absorption peak at the wavelength of1743cm-1was obvious,it was characteristic absorption peak ester-bond’s. The result showed that the sucrose ester was obtained. The methods of separation of SE and materials’recycling were also built.(2) By the single factor experiments, the effects of the reaction system, the kind of sugar, sugar content, temperature, molecular sieve and time on sugar ester transformation were investigated. On the basis of single factor experiments, the perpendicular experiments were designed to optimize the condition. The optimal conditions was built when the reaction was carried out in the tert-butyl alcohol with0.6mol/L of lauric acid,0.08mol/L of sucrose, 30g/L of lipase and50g/L molecular sieves, at50℃for65hours. The remains of lipase activities was measured,after five times’ reaction on optimal conditions, the remains activity of lipase was62.5%.(3) In the non-aqueous lipase catalytic system, the common heat was instead of microwave. The lauroyl sucrose ester was obtained by assisted enzymatic method. By the single factor experiments, the effects of microwave power, molecular sieve content, time on sugar ester transformation was investigated. On the basis of single factor experiments, the perpendicular experiments were designed to optimize the condition. The optimal conditions was built when the reaction was carried out in the tert-butyl alcohol with0.6mol/L of lauric acid,0.08mol/L of sucrose,30g/L of lipase and15g/L of molecular sieves, at50℃with microwave of200W power for25min. After three times’ reaction, the remains activity of lipases was52.4%.The product was analysis by TLC and FT-IR.(4) The surfactant properties of the product which is synthesis by lipase in non-aqueous was measured. Compared to food grade SE,the emulsifying and foaming ability of the product was better.