부산대학교 도서관

Polyhydroxyalkanoates (PHAs) are biological polyesters that are produced by a wide variety of bacteria as an intracellular storage material of carbon and energy. PHAs have attracted industrial attention because of their potential use as practical biodegradable thermoplastics. Xylose is the most abundant sugar in the hemicelluloses of hardwoods and crop residues, and the efficient production of PHA from xylose reduces production cost. Certain bacteria can produce PHA from xylose; however, high production rate and yield of PHA from xylose have not been achieved. Some lactic acid bacteria are capable of efficiently fermenting xylose into lactic acid and acetic acid at high production rate. These organic acids produced from xylose can be used as carbon sources for R.eutropha, the most famous PHA producer, and able to convert into PHA. We investigated the feeding strategy of the mixture of lactic acid and acetic acid for fed-batch culture of R. eutropha to efficiently produce PHA from xylose by way of such organic acids. Vegetable oils are also desirable feedstock for PHA production. Since vegetable oils compose a much higher number of carbon atoms per weight than glucose and sucrose, the yield coefficients of PHA production from vegetable oils are as high as over 0.7 g-PHA per g-vegetable oils (sugars are in the range of 0.2-0.4 g-PHA per g-substrate). To produce PHA from soybean oil as a model substrate, recombinant R. eutropha was generated and cultured in 10-l laboratory scale fermentor. As a result, high dry cell weight (138 g/l) and high PHA content (74% w/w) were achieved after 96 h of cultivation, with high production yield ranging from 0.72 to 0.74 g-PHA per g-soybean oil. Furthermore, we evaluated whether PHA production form vegetable oils is environmentally friendly bioprocess by life cycle assessment-based approach.