Utilization of simultaneous saccharification and fermentation residues as feedstock for lipid accumulation in Rhodococcus opacus

Abstract

Use of oleaginous microorganisms as “micro-factories” for accumulation of single cell oils for biofuel production has increased significantly to mitigate growing energy demands, resulting in efforts to upgrade industrial waste, such as second-generation lignocellulosic residues, into potential feedstocks. Dilute-acid pretreatment (DAP) is commonly used to alter the physicochemical properties of lignocellulosic materials and is typically coupled with simultaneous saccharification and fermentation (SSF) for conversion of sugars into ethanol. The resulting DAP residues are usually processed as a waste stream, e.g. burned for power, but this provides minimal value. Alternatively, these wastes can be utilized as feedstock to generate lipids, which can be converted to biofuel. DAP-SSF residues were generated from pine, poplar, and switchgrass. High performance liquid chromatography revealed less than 0.13% monomeric sugars in the dry residue. Fourier transform infrared spectroscopy was indicative of the presence of lignin and polysaccharides. Gel permeation chromatography suggested the bacterial strains preferred molecules with molecular weight ~ 400–500 g/mol. DAP-SSF residues were used as the sole carbon source for lipid production by Rhodococcus opacus DSM 1069 and PD630 in batch fermentations. Depending on the strain of Rhodococcus employed, 9–11 lipids for PD630 and DSM 1069 were observed, at a final concentration of ~ 15 mg/L fatty acid methyl esters (FAME) detected. Though the DAP-SSF substrate resulted in low FAME titers, novel analysis of solid-state fermentations was investigated, which determined that DAP-SSF residues could be a viable feedstock for lipid generation.Electronic supplementary materialThe online version of this article (doi:10.1186/s13568-017-0484-0) contains supplementary material, which is available to authorized users.

Editorial: Advancements in Biomass Recalcitrance: The Use of Lignin for the Production of Fuels and Chemicals

“…these efforts, the conversion of lignin to chemicals and fungible fuels for ground and aviation transportation is being aggressively developed using thermal and/or catalytic processes (Ben and Ragauskas, 2011;Bi et al, 2015). As an alternative to these chemical technologies, the power of biology is also being investigated to convert lignin to fatty acids and esters using Rhodococcus (Le et al, 2017), and Pseudomonas putida for PHAs (Liu et al, 2017), to name just a few promising pathways.…”

Discovery of potential pathways for biological conversion of poplar wood into lipids by co-fermentation of Rhodococci strains

“…The bioconversion from lignin to lipid by R. opacus utilizing ultrasonicated ethanol organosolv lignin with the yield of 0.004 g/g substrate and 4.08% (based on CDW) has been reported in 2013 [ 1 ]. The residues from dilute-acid pretreatment mainly consisting of lignin and polysaccharides supported the lipid titer of around 0.015 g/L by R. opacus PD630 or DSM 1069 [ 30 ].…”

A concerted systems biology analysis of phenol metabolism in Rhodococcus opacus PD630

“…Recently, research groups are attempting to develop microbial hosts with improved tolerance to aromatic compounds for fermentation of lignocellulose-derived sugars and lignin-derived aromatic compounds (Abdelaziz et al, 2016;Ragauskas et al, 2014;Janusz et al 2017). In particular, lignin-rich streams have been utilized to generate lipid-based biofuels (i.e., waste-to-fuel applications) (Le et al, 2017;Yaguchi et al, 2017).…”