Biomass pyrolysis liquid to citric acid via 2-step bioconversion

Abstract

BackgroundThe use of fossil carbon sources for fuels and petrochemicals has serious impacts on our environment and is unable to meet the demand in the future. A promising and sustainable alternative is to substitute fossil carbon sources with microbial cell factories converting lignocellulosic biomass into desirable value added products. However, such bioprocesses require tolerance to inhibitory compounds generated during pretreatment of biomass. In this study, the process of sequential two-step bio-conversion of biomass pyrolysis liquid containing levoglucosan (LG) to citric acid without chemical detoxification has been explored, which can greatly improve the utilization efficiency of lignocellulosic biomass.ResultsThe sequential two-step bio-conversion of corn stover pyrolysis liquid to citric acid has been established. The first step conversion by Phanerochaete chrysosporium (P. chrysosporium) is desirable to decrease the content of other compounds except levoglucosan as a pretreatment for the second conversion. The remaining levoglucosan in solution was further converted into citric acid by Aspergillus niger (A. niger) CBX-209. Thus the conversion of cellulose to citric acid is completed by both pyrolysis and bio-conversion technology. Under experimental conditions, levoglucosan yield is 12% based on the feedstock and the citric acid yield can reach 82.1% based on the levoglucosan content in the pyrolysis liquid (namely 82.1 g of citric acid per 100 g of levoglucosan).ConclusionThe study shows that P. chrysosporium and A. niger have the potential to be used as production platforms for value-added products from pyrolyzed lignocellulosic biomass. Selected P. chrysosporium is able to decrease the content of other compounds except levoglucosan and levoglucosan can be further converted into citric acid in the residual liquids by A. niger. Thus the conversion of cellulose to citric acid is completed by both pyrolysis and bio-conversion technology.

Conversion efficiency of bioethanol from levoglucosan was improved by the newly engineered Escherichia coli

“…It has been reported by our previous publication that 68.8 wt % biooil can be harvested from the corn stover material, while levoglucosan accounted for $17.5 wt % of the bio-oil, 42 implying that levoglucosan yield was $12.0 wt % of our starting corn stover. In this study, the recovery yield of levoglucosan crystal was 74.0% (detected by HPLC), implying that 8.9% (89 g levoglucosan per 1 kg corn stover) pure levoglucosan could be obtained from the starting corn stover material.…”

“…However, when all the levoglucosan substrate present in the bio-oil was fermented by the engineered strains in situ, the ethanol yield could be improved to 17.07-gallon ethanol per ton corn stover. Furthermore, in light of the fact that levoglucosan can reach a yield of 70 wt % of the cellulose feedstock 12 and the cellulose component of the corn stover ranges from 40 to 60 wt % 43 (it is 41.46 wt % in this article 42 ), an improved process in the future could produce levoglucosan with a maximum of 42 wt % of the corn stover, and accordingly the ethanol yield of our engineered E. coli could achieve as high as 59.75-gallon ethanol per ton corn stover.…”

Transformation of Lignocellulosic Biomass into Sustainable Biofuels: Major Challenges and Bioprocessing Technologies

“…Chemical detoxification could generate waste and utilize a large amount of reagents (Yang et al, 2014). To overcome this Yang et al, used biological detoxification strategy to inactivate the toxicity of inhibitors in the sugar-rich phase of bio-oil by using Phanerochaete chrysosporium, which can mineralize lignin and other related molecules.…”

“…To overcome this Yang et al, used biological detoxification strategy to inactivate the toxicity of inhibitors in the sugar-rich phase of bio-oil by using Phanerochaete chrysosporium, which can mineralize lignin and other related molecules. So, after the successful removal of toxins of sugars, it was fermented to citric acid by A. niger CBX-209 (Yang et al, 2014). Thus, the conversion of cellulose to citric acid was completed by both pyrolysis and bio-conversion technology.…”

Microwave‐assisted exfoliation of graphite using 1‐allyl‐pyridinium‐based ionic liquids and application to solid acid catalysts

“…10 Another method involving the use of sulfuric acid presents issues related to its large-scale application, such as potential corrosion of reactors; difficulties in terms of catalyst recovery and waste acid treatment also exist. 11 The use of solid acid catalysts has been proposed to resolve these issues because they can be used repeatedly and easily separated. 12 Metal oxides, 13 polymer-based acids, 14 heteropoly acids, 15 H-form zeolites, 16 and supported metal catalysts 17 have been investigated for saccharification.…”