Use of a nylon manufacturing waste as an industrial fermentation substrate

Nonvolatile residue (NVR), a waste stream from the manufacture of nylon 6'6', contains mainly small carboxylic acids and alcohols, making it a potential fermentation substrate. Above a concentration of 1.3% (wt/vol), NVR inhibited the growth of all microorganisms tested. The most inhibitory of the major NVR components were the monocarboxylic acids (C(4) to C(6)) and epsilon-caprolactone. The inhibitory effects of NVR could be avoided by using a carbon-limited chemostat. Microorganisms were found that could use all of the major NVR components as carbon and energy sources. One such organism, Pseudomonas cepacia, was grown in a carbon-limited chemostat with a medium feed concentration of 20.5 g of NVR liter. At a dilution rate of 0.14 h the yield of biomass (Y(x/s), where x is biomass produced and s is substrate used) from NVR was 18% (neglecting the water content of NVR). It was concluded that NVR would be a suitable carbon source for certain industrial fermentation processes such as the production of poly-beta-hydroxybutyric acid.