18D-26

P. CHAKRABORTY¹, W. Gibbons², K. Muthukumarappan³, and J. Javers². (1) Agriculture and Biosystems Engineering, South Dakota State Univ., 1400 North Campus Drive, Brookings, SD 57007, (2) Biology/Microbiology, South Dakota State Univ., 1400 North Central Drive, Brookings, SD 57007, (3) Dept. of Agricultural & Biosystems Engineering, South Dakota State Univ., PO Box 2120, Brookings, SD 57007

Polyhydroxyalkanoates (PHAs) are biopolymers that can be completely degraded to carbon dioxide and water by microbial activity, so they can be used to replace non-biodegradable plastics. The aim of this research is to use Ralstonia eutropha to produce PHA from condensed corn solubles (CCS), a low value byproduct of ethanol industry. Ralstonia eutropha was acclimated and then grown in different concentrations (80 g/l, 240g/l, 400g/l and 700g/l) of CCS media. Growth rates in these media were compared to that in a defined media. The medium with the optimum concentration of CCS was supplemented to different levels of carbon: nitrogen (C: N) ratios (5:1, 10:1 and 15:1) so as to produce a concentrated cell mass (CCM). Initially the trials were conducted in shake flasks fitted with an aerator and an agitator. Finally the organism was grown in the media with optimum concentration of CCS and C:N ratio in a bench top 3 L fermentor, using an agitation rate of 250 rpm, an aeration rate of 1L/L/min, at 37^oC and pH 7. The CCM produced was then subjected to nutrient limitation to trigger PHA production. To produce short chain length (scl) PHA, volatile fatty acids (VFA), namely acetic, butyric and propionic, will be fed individually or in combination to Ralstonia eutropha growing in CCS. The VFAs are the product of cellulose digestion done in an artificial rumen. The scl PHA produced will then be extracted from the cells using Super Critical Fluid Extraction (SFE). The maximum cell number (10⁹-10¹⁰ cfu/ml) was obtained in medium with CCS concentration of 400 g/l and C:N ratio of 10:1. We expect that the feeding of propionic acid will produce highest PHA yield. The purpose of this study is to reduce the cost of large scale production of PHA.

Session 18D, Food Microbiology: General
2:00 PM - 5:30 PM, Sunday PM Room Hall I-2

2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana