(194z) Suite of Bacteria from the Enterobacter Genus Suitable for Lignin Degradation

Nicpon, J., South Dakota School of Mines and Technology
Shende, A., South Dakota School of Mines and Technology
Shende, R., South Dakota School of Mines and Technology
Lignin is an amorphous three dimensional biopolymer composed of phenyl propanoid units linked by the recalcitrant C-C and C-O bonds. It constitutes between 15-30% of the lignocellulosic biomass. Biofuel industries which are mostly focused on conversion of the celluloses to biofuels are expected to generate large quantities of lignin waste. From the point of waste remediation and carbon efficiency, it is necessary to identify routes to covert lignin into valuable products. Here we explore a few species from the Enterobacter genus suitable for lignin bioconversion.The adaptive plasticity of the Enterobacter species to switch between aerobic, anaerobic respiration and fermentation has enabled survival in lignin rich ecological niches such as the soil, subsurface, sewage and also as epiphytes and plant pathogens.Recently, several novel lignolytic Enterobacter species were isolated from soil, paper and pulp waste and bamboo slips. We have isolated the lignin degrading Enterobacter RC202 from 4850 feet deep subsurface soil surrounding decomposing wood. The Enterobacter RC202 and other lignolytic bacterial species from the Enterobacter genus can utilize complex carbon substrates such as the kraft lignin and lignin model compounds as sole sources of carbon. The bacteria use mechanisms such as demethoxylation, dehydroxylation and aromatic ring cleavage to partial degrade or mineralize these compounds. We have compared the diverse approaches used by Enterobacter cloacae subsp. Cloacae ATCC® 35929™ , 35930™, Enterobacter cloacae subsp. dissolvens ATCC® 23373™ and the Enterobacter RC202 species to utilize selected aromatic compounds as sole carbon sources under aerobic and anaerobic conditions. A temporal product profile was developed from the HPLC and GC-MS analysis of spent culture media. Utilization of kraft lignin and lignin derived aromatic compounds by the lignin degrading Enterobacter species and application of these species in lignin valorization will be discussed.