Esterification Of The Polyol Catalyzed By Whole-Cell Catalyst And Its Polymers’ Application On Papermaking

Polyhydroxy esters are widely used in cosmetics, food, pharmaceutical and other industries, due to their wide range of critical micelle concentration(CMC) and hydrophilic- lipophilic balance(HLB) value. C urrently, most of the polyhydroxy esters are synthesized by chemical synthesis. Those methods show poor selectivity with several by-products and are environmentally unfriendly. Enzymatic synthesis use enzymes as catalysts for catalytic synthesis of polyhydroxy esters, which show many strong points, such as mild reaction conditions, high selectivity, environmental friendliness, etc. However, the high cost of these methods greatly hindered their large-scale industrial applications. The whole cells can provide a natural environment for enzyme location which protects the enzymes from a rapid deactivation in non-aqueous solvents and accounts for a large part of the enzyme cost.In this dissertation, whole cell biocatalysts were applied for the first time in polyhydroxy ester synthesis. Aarabinose and sucrose were used as the typical sugar compounds and vinyl methacrylateas was acyl donor. Meanwhile, the effects of reaction conditions such as the amount of whole cell catalyst, substrate molar ratio and temperature on the reaction were discussed. The optimal esterification conditions were determined.In seven different sources of microorganisms studied, Pseudomonas stutzeri showed the highest catalytic activity for the synthesis of arabinose ester, with the substrate conversion being of 48.3%. In the pure organic solvents, the catalytic activities of the cells were low. When binary solvents mixture was used, especially in tert-amyl alcohol-dimethyl sulfoxide system, the conversion rate was improved significantly. The optimal reaction conditions were determined as follows: ratio of dimethyl sulfoxide to tert-amyl alcohol 20:80(v/v), reaction temperature 50 ℃, whole cell catalyst dosage 80 mg ? m L-1, and ratio of vinyl methacrylate to arabinose 10:1. Under the above- mentioned conditions, the conversion rate of the esterification reaction reached the maximum value of 75.9%. In seven different sources of microorganisms studied, Pseudomonas stutzeri showed the highest catalytic activity for the synthesis of sucrose ester, with the substrate conversion being of 36.7%. In the pure organic solvents, the catalytic activities of the cells were low. When binary solvents mixture was used, especially in tert-amyl alcohol-dimethyl sulfoxide system, the conversion rate was improved significantly. The optimal reaction conditions were determined as follows: ratio of dimethyl sulfoxide to tert-amyl alcohol 20:80(v/v), reaction temperature 50 ℃, whole cell catalyst dosage 80 mg ? m L-1, and ratio of vinyl methacrylate to arabinose 10:1. Under the above- mentioned conditions, the conversion rate of the esterification reaction reached the maximum value of 68.4%. Study found that, after the whole-cell catalyst reused six times, which can reach 88% relative activity proved a good operational stability of its operational stability.The sucrose ester monomers achieved with the whole-cell biocatalysis were then used for polymerization with acrylamide in aqueous solutions. The reaction conditions were optimized and the best amount of sucrose ester, amount of initiator, the reaction temperature and shaking speed were 1%,1%, 35 ℃ and 200 rpm, respectively. IR spectra showed that sucrose monomer had been grafted onto the polyacryla mide. The sucrose-containing polymers prepared via above- mentioned polymerization were added into fiber suspension as dry strength agent. Results showed that the physical properties of the paper, such as tensile index, tear index and burst index, were significantly improved. When the added amount of sucrose polymer was 0.6%, the paper tensile index showed the best effect to improve 25.8%; when the added of sucrose polymer was 0.8%, the paper tear index showed the best effect to improve 21.8%; when the added amount of sucrose polymer was 0.8%, the bursting of the paper showed best effect to improve 38.7%.The result demonstrated Sucrose-containing monomer polymer has an excellent reinforcing effect.