Microbial conversion of pyrolytic products to biofuels: a novel and sustainable approach toward second-generation biofuels

Abstract

This review highlights the potential of the pyrolysis-based biofuels production, bio-ethanol in particular, and lipid in general as an alternative and sustainable solution for the rising environmental concerns and rapidly depleting natural fuel resources. Levoglucosan (1,6-anhydrous-β-D-glucopyranose) is the major anhydrosugar compound resulting from the degradation of cellulose during the fast pyrolysis process of biomass and thus the most attractive fermentation substrate in the bio-oil. The challenges for pyrolysis-based biorefineries are the inefficient detoxification strategies, and the lack of naturally available efficient and suitable fermentation organisms that could ferment the levoglucosan directly into bio-ethanol. In case of indirect fermentation, acid hydrolysis is used to convert levoglucosan into glucose and subsequently to ethanol and lipids via fermentation biocatalysts, however the presence of fermentation inhibitors poses a big hurdle to successful fermentation relative to pure glucose. Among the detoxification strategies studied so far, over-liming, extraction with solvents like (n-butanol, ethyl acetate), and activated carbon seem very promising, but still further research is required for the optimization of existing detoxification strategies as well as developing new ones. In order to make the pyrolysis-based biofuel production a more efficient as well as cost-effective process, direct fermentation of pyrolysis oil-associated fermentable sugars, especially levoglucosan is highlly desirable. This can be achieved either by expanding the search to identify naturally available direct levoglusoan utilizers or modify the existing fermentation biocatalysts (yeasts and bacteria) with direct levoglucosan pathway coupled with tolerance engineering could significantly improve the overall performance of these microorganisms.

Identification and characterization of Burkholderia multivorans CCA53

“…At the enzymatic hydrolysis step, cellulose and hemicellulose are converted into saccharified solution, which includes fermentable sugars, aldehyde inhibitors and lignin. In the fermentation step, the fermentable sugars are used as carbon sources by engineered Escherichia coli , Saccharomyces cerevisiae or other microorganisms [35, 36]. Although aldehyde inhibitors inhibit microbial growth and interfere with subsequent fermentation, these compounds can be chemically or enzymatically detoxified [34, 37].…”

“…Although aldehyde inhibitors inhibit microbial growth and interfere with subsequent fermentation, these compounds can be chemically or enzymatically detoxified [34, 37]. However lignin is not effectively utilized by the aforementioned microorganisms, causing the yield to be low [35, 36]. Microbial degradation of lignin has been primarily studied in brown- and white-rot fungi.…”

“…Several Burkholderia species cannot assimilate d -lactose or d -maltose [29], but B. multivorans CCA53 was able to use all of these disaccharides as carbon sources, which means that B. multivorans CCA53 could be a useful strain for production of second-generation biofuels [35, 36]. Moreover, we think that B. multivorans CCA53 may have other advantages for industrial application beyond utilization of lignin.…”

Draft Genome Sequence of Pseudomonas sp. Strain CCA1, Isolated from Leaf Soil

“…Thus, effective utilization of lignin could support second-generation biofuel production from lignocellulosic biomass (2). Phanerochaete chrysosporium , Rhodococcus erythropolis , and Streptomyces coelicolor are able to assimilate lignin as a carbon source (3).…”

Pretreatment strategies for microbial valorization of bio‐oil fractions produced by fast pyrolysis of ash‐rich lignocellulosic biomass

“…An alternative application of lignocellulosic-based biooil and its fractions is its use as a carbon source for microbial cultivation (Arnold, Moss, Henkel, & Hausmann, 2017;Islam, Zhisheng, Hassan, Dongdong, & Hongxun, 2015;Jarboe, Wen, Choi, & Brown, 2011). Bio-oil is mainly composed of water, pyrolytic lignin, and a wide variety of organic components such as organic acids, sugars, alcohols, aldehydes, ketones, and phenolic components (Piskorz, Scott, & Radlein, 1988).…”