Production of biological polymers from organic wastes

Biologically-produced polymers, from microbial fermentation are naturally b iodegradable and are potential environment-friendly substitutes for some sy nthetic plastics. However, broader applications are restricted by the high production costs and limitations in physical and mechanical properties. In this study, activated sludge bacteria in a conventional wastewater treatmen t system treating a wastewater that contained organic pollutants, were indu ced by nitrogen deficiency to accumulate intracellular storage polymers, wh ich can be extracted as a low-cost source of biodegradable plastics. Chroma tographic analysis of the extracted polymers revealed a composition of poly -hydroxyalkanoate and a number of related co-polymers. Alcaligene spp. in t he activated sludge microbial consortium was identified as the main genus a ccumulated these polymers. When the C:N ratio was increased from 20 to 140, the specific polymer yield increased to a maximum of 0.39 g polymer/g dry cell while specific growth yield decreased to 0.26 g dry cell/g carbonaceou s matter consumed. The highest overall polymer production yield of 0.11 g p olymer/g carbonaceous matter consumed was achieved when the C:N ratio was m aintained at a nitrogen-deficient level of 100. The specific polymer yield in the isolated Alcaligene spp. cells were as high as 0.7 g polymer/g dry c ell mass. The composition of the co-polymers, and hence the physical and me chanical properties, could be controlled by manipulating the influent organ ic compositions.