Process kinetic studies of biohydrogen production by co-fermentation of fruit-vegetable wastes and cottage cheese whey

Abstract

Hydrogen (H-2) is considered as fuel for future and its biological production from renewable feedstocks is very promising. Dark fermentation of fruit-vegetable waste (FVW) and cottage cheese whey (CCW) for the production of H-2 constitutes a promising way for combining energy generation and lignocellulosic waste management. In this work, process kinetics of biohydrogen production via dark fermentation of FVW and CCW by pretreated anaerobic sludge inocula were investigated. To inhibit H-2 consuming methanogens, the effects of various inoculum pretreatment, viz., 2-bromoethanesulfonate, heat-shock, acid, alkali, UV, and ultrasonication on H-2-production were investigated which revealed 2-bromoethanesulfonate, heat-shock and acid-treated inoculum resulted in maximum bioH(2) production and yield of 118.12 +/- 1.05, 93.37 +/- 1.3, 96.32 mMol/L and 1.66, 1.22 +/- 0.01, 1.39 +/- 0.02 mMol/gCOD(initial), respectively. The effects of system initial pH, substrate to inoculum (S-0/X-0) and carbon to nitrogen (C/N) ratio on H-2-production were evaluated which revealed maximum H-2 production and yield could be achieved at pH 7, S-0/X-0 of 10.6 g(COD)/g(VS), and C/N 26.8. Modified Gompertz model and Modified Logistic model were used to define various kinetic parameters pertaining to cumulative H-2-production which showed high R-2 values (>= 0.98). The influence of pH on H-2 and ethanol/volatile fatty acids production kinetics were evaluated using Andrew's and Ratkowsky's model showing relatively good R-2 values (?0.62). Remarkably high production of ethanol (2.43 +/- 028 mg/L) was noticed alongside H-2 production at pH 7 suggesting that bioethanol can be recovered at the end of fermentative H-2 production. Terminal Restriction Fragment Length Polymorphism and 16s rDNA sequencing revealed dominance of 9 bacterial species such as Escherichia coll. Clostridium butyric um, Streptococcus henryi. and 6 others uncultured bacteroides. This research determined different kinetic parameters for an enhanced H-2 production strategy by co-fermentation of FVW and CCW providing an understanding of process behavior which will in turn help in the upscaling of the H-2-production processes.