Hydrogen from food processing wastes via photofermentation using Purple Non-sulfur Bacteria (PNSB) – A review

Purple non-sulfur bacteria (PNSB) mediated production of biohydrogen utilizing solid food waste and food processing wastewater possess enormous potential to be implemented as an ideal "green energy technology". This paper reviews the current state-of-the-art utilization of solid wastes and wastewaters of several food and beverage processing industries in photofermentative H2 production systems. Detailed accounts of the complex composition of various solid food wastes and food processing wastewaters along with the pretreatments used for enhancement of H2 production by PNSBs have been presented. Factors like compositional complexity, presence of inhibitory compounds and resistance to light penetration are identified as the prime bottlenecks hindering the efficient utilization of food waste and wastewaters in photofermentative H2 production. Genetic manipulation of the PNSBs to overcome the inherent metabolic complications has been discussed as a probable amelioration strategy for enhancement of H2 yield. Based on profound discussions the scopes for upgradation of the photofermentative biohydrogen systems using food waste/wastewater have been highlighted and recommended for the overall enhancement of the sustainability of the processes.