Research On Polymalic Acid Production By Aureobasidum Pullulan Fermentation With Biomass Feedstock

Poly (B-malic acid)(PMA) is a water-soluble polyester that is formed by malic acid as only monomer and linked each other with ester bond. PMA have a lot of excellent characteristics, including:highly water-soluble, biocompatible, biodegradable, bio-absorbable, non-immunogenic and can be chemically modified, etc. PMA being developed for pharmaceutical carrier, microcapsule materials, biomedical materials, cosmetics, food packaging materials, and surface active agent, etc based on the characteristics.Currently, there are two methods use for synthesis of PMA including chemical synthesis and biological fermentation. Chemical synthesis has many disadvantages, such as the reaction conditions are harsh, the lower the molecular weight of the product and the product separation and purification is so difficult. However the biological fermentation has many advantages, for example the product is relatively pure, high molecular weight, mild reaction conditions, but it could synthesis β-poly malic acid only. In recent years, people are more inclined to biological fermentation synthesis of PMA. The article against the problem of PMA production use Microorganism fermentation. For example, the level of fermentation couldn’t meet the demand of the industrial production. We use biomass resources to product PMA by (A. pullulan FMT1801) and the main contents are as follows:1. We took the fresh sweet potato as raw material, combined acid hydrolysis with enzymatic hydrolysis to prepare sweet potato hydrolyzate. We have investigated the effect of the initial concentration of hydrolyzate, nitrogen source, initial pH, and metabolic intermediates to synthesis of PMA. The results show that the best concentration of hydrolyzate, nitrogen source, initial pH, and metabolic intermediates is120g/l、NH4NO3、6.0 and Citric acid7.5g/l respectively. We found that the production, productivity and yield of PMA is16.59g/L、0.14g/l.h and0.20g/g。respectively under this condition in shake flask. And the result of batch fermentation shows that the production, productivity and yield of PMA is29.55g/L、0.25g/L.h、0.28g/g respectively. We have also found that the result of fed-batch fermentation shows that the production, productivity and yield of PMA is51.37g/L、0.31g/L.h、0.20g/g respectively. The result is58.93g/L、0.35g/L.h、0.18g/g respectively when we use a FBB. It is much higher than fed-batch fermentation.2We have investigated the effect of the different acid neutralizer to synthesis of PMA. The result shows that the carbon dioxide evolution rate (CER) and respiratory quotient (RQ) is decreased gradually. This shows that the fixation of CO2play an important role during the synthesis of PMA. Take three different acid neutralizer to regulate the pH of the fermentation process, the result shows that the20%Na2CO3is the best, the best production, productivity and yield of PMA is38.13g/l、0.53g/l.h、0.61g/g respectively when use20%Na2CO3to regulate the pH. We have investigated the effect of the cofactor of pyruvate carboxylase to synthesis of PMA also In shake flask. The result shows that add biotin(70mg/l) is good for synthesis of PMA. the production, productivity and yield of PMA is23.14g/L、0.24g/l.h、0.32g/g respectively and the control group is19.22g/L、0.20g/l.h、0.22g/g respectively. These results suggest that CO2play an important role during the synthesis of PMA as a greenhouse gas and carbon.3We took the corn cob as raw material, combined acid hydrolysis with enzymatic hydrolysis to prepare corn cob hydrolyzate. It is reported that there are furfural,5-(hydroxymethyl) furfural and other toxic substances in corn cob hydrolyzate. We use FBB to immobilize A. pullulan FMT1801for product PMA. The Initial concentration of corn cob hydrolyzate is increased gradually (110～150g/l). Each concentration is three cycle. The result shows that the consumption of sugar is accelerate gradually and the production of PMA is improve. We have isolated domesticated strains further, find that the tolerance of domesticated strains to corn cob hydrolyzate is better than original strain obviously.