(131d) Biodegradation Characteristics of Wastewater Using Different E. coli Strains

Cheese whey is produced in huge amounts during cheese manufacturing causing serious pollution problems. The main objective of this study is to investigate the biodegradation of cheese whey lactose using different bacterial strains, namely: E. coli strain as parental cells, VHb-expressing E. coli that is transformed with Vitreoscilla hemoglobin gene, vgb (E. coli:pUC8:16), and E. coli harboring a pUC9 plasmid (E. coli:pUC9). Batch fermentation experiments were performed at controlled temperature with different conditions such as initial whey lactose concentration, carbon and nitrogen sources, and yeast extract concentration. The VHb strain was found to be more efficient in whey lactose biodegradation than the other vgb-lacking strains.  The lactic acid was detected as a product of cheese whey lactose biodegradation. Maximum growth and lactic acid production of VHb-expressing E. coli cells was achieved by using a mixture of 20% whey and 80% minimal salt medium in the growth culture. Under optimum growth conditions, a vgb-bearing strain was slightly more efficient than Lactobacillus acidophilus based on lactic acid production measurements. Contrary to Monod’s, Haldane’s growth kinetics model gave a good fit to the growth kinetics data. Kinetic constants of the Haldane equation were μ_m= 0.5573 h^-1, K_s = 4.8812 g/L, K_I = 53.897 g/L. Biomass growth was well described by the logistic equation while Luedeking-Piret equation defined the product formation kinetics. Substrate consumption was explained by production rate and maintenance requirements. In simulation studies including the Haldane model, an evident agreement was observed between measured and calculated biomass, product, and substrate concentrations.