Potential of biofilm-based biofuel production.

Biofilm technology has been extensively applied to wastewater treatment, but its potential application in biofuel production has not been explored. Current technologies of converting lignocellulose materials to biofuel are hampered by costly processing steps in pretreatment, saccharification, and product recovery. Biofilms may have a potential to improve efficiency of these processes. Advantages of biofilms include concentration of cell-associated hydrolytic enzymes at the biofilm-substrate interface to increase reaction rates, a layered microbial structure in which multiple species may sequentially convert complex substrates and coferment hexose and pentose as hydrolysates diffuse outward, and the possibility of fungal-bacterial symbioses that allow simultaneous delignification and saccharification. More importantly, the confined microenvironment within a biofilm selectively rewards cells with better phenotypes conferred from intercellular gene or signal exchange, a process which is absent in suspended cultures. The immobilized property of biofilm, especially when affixed to a membrane, simplifies the separation of biofuel from its producer and promotes retention of biomass for continued reaction in the fermenter. Highly consolidated bioprocessing, including delignification, saccharification, fermentation, and separation in a single reactor, may be possible through the application of biofilm technology. To date, solid-state fermentation is the only biofuel process to which the advantages of biofilms have been applied, even though it has received limited attention and improvements. The transfer of biofilm technology from environmental engineering has the potential to spur great innovations in the optimization of biofuel production.