|Ashby, Richard - Rick|
Submitted to: Annual Meeting and Expo of the American Oil Chemists' Society
Publication Type: Abstract Only
Publication Acceptance Date: 2/15/2006
Publication Date: 4/30/2006
Citation: Solaiman, D., Ashby, R.D., Zerkowski, J.A., Hotchkiss, A.T., Foglia, T.A., Marmer, W.N. 2006. Bioconversion of soy-based feedstocks into biopolymers and biosurfactants [abstract]. Annual Meeting and Expo of the American Oil Chemists' Society. p. 14.
Technical Abstract: Poly(hydroxyalkanoates) (PHAs) are biodegradable polymers produced and intracellularly stored by many bacteria and archaea, and sophorolipids (SLs) are extracellular biosurfactants synthesized and secreted by several yeast species. Both PHA and SL are environmentally desirable biomaterials that can be produced by biotechnological processes using renewable resources from agriculture as starting materials. PHAs and SLs are variously investigated for potential applications in thermoplastics, adhesives, biomedical and engineering devices, packaging materials, cleaning solutions, cosmetic creams, antimicrobial formula, and petro-oil recovery and oil clean-up processes. The costs of production for PHA and SL, however, must be lowered to make them economically competitive. One way to achieve this is to use inexpensive fermentative substrates as the starting materials in the production process. In this paper, we describe our investigation on the use of a surplus and low-cost soy-based feedstock, i.e., soy molasses, for the fermentative production of medium-chain-length (mcl-)PHA and SL. We first screened a collection of Pseudomonas strains for their ability to grow on, and to utilize the major sugars of, soy molasses. We identified P. corrugata and P. chlororaphis as candidate strains, and selected P. corrugata for further characterization on the production of medium-chain-length PHA from soy molasses. Genetic engineering work is initiated to enable the utilization of stachyose and raffinose in the soy molasses by P. corrugata to increase cell density and PHA yields. We also had previously shown that Candida bombicola synthesized SL at a yield of 21 g/l when grown on soy molasses. We have now characterized the kinetics of consumption of the two co-substrates used in the process, i.e., oleic acid and the sugars of soy molasses, and showed that the consumption of oleic acid preceded the utilization of the sugars of soy molasses. The information lays the groundwork for devising a fed-batch strategy to optimize substrate utilization and product yield. Fed-batch strategy is a fermentation approach in which substrates or nutrients are continuously added at a certain rate to replenish their consumption.