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Among the products of pyrolysis is an aqueous phase (AP), which contains a significant fraction of carbon but is too dilute to make recovery of this organic content cost-effectively. This study was to explore the use of AP for anaerobic digestion. Different treatment methods including overliming, Fenton's reagent oxidation, bleaching and activated carbon adsorption were investigated to reduce toxicity of AP. Overliming treatment increased biogas production up to 32-fold compared to non-treated AP. Enhancing the tolerance of the bacterial and archaeal community to the AP toxicity was also attempted with a directed evolution method, resulting the microbes' tolerance to AP from 5% to 14%. Directed evolution resulted a major bacterial taxa as Cloacimonetes, Firmicutes, and Chloroflexi, while shifted the predominant archaea shifted from acetoclastic to hydrogenotrophic methanogens. Collectively, the results demonstrated that combining feedstock treatment and directed evolution of the microbial community is an effective way for AP anaerobic digestion., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Fermentative production of styrene from glucose has been previously demonstrated in Escherichia coli. Here, we demonstrate the production of styrene from the sugars derived from lignocellulosic biomass depolymerized by fast pyrolysis. A previously engineered styrene-producing strain was further engineered for utilization of the anhydrosugar levoglucosan via expression of levoglucosan kinase. The resulting strain produced 240 ± 3 mg L styrene from pure levoglucosan, similar to the 251 ± 3 mg L produced from glucose. When provided at a concentration of 5 g L, pyrolytic sugars supported styrene production at titers similar to those from pure sugars, demonstrating the feasibility of producing this important industrial chemical from biomass-derived sugars. However, the toxicity of contaminant compounds in the biomass-derived sugars and styrene itself limit further gains in production. Styrene toxicity is generally believed to be due to membrane damage. Contrary to this prevailing wisdom, our quantitative assessment during challenge with up to 200 mg L of exogenously provided styrene showed little change in membrane integrity; membrane disruption was observed only during styrene production. Membrane fluidity was also quantified during styrene production, but no changes were observed relative to the non-producing control strain. This observation that styrene production is much more damaging to the membrane integrity than challenge with exogenously supplied styrene provides insight into the mechanism of styrene toxicity and emphasizes the importance of verifying proposed toxicity mechanisms during production instead of relying upon results obtained during exogenous challenge. [ABSTRACT FROM AUTHOR]

Acetic acid derived from fast pyrolysis of lignocellulosic biomass is a promising substrate for microalgae fermentation for producing lipid-rich biomass. However, crude pyrolytic acetic acid solution contains various toxic compounds inhibiting algal growth. It was hypothesized that such an inhibition was mainly due to the cell membrane damage. In this work, the cell membrane property of algal cells was evaluated at various conditions to elucidate the mechanisms of inhibition caused by the pyrolytic substrate solution. It was found that acetic acid itself served a carbon source for boosting algal cell growth but also caused cell membrane leakage. The acetic acid concentration for highest cell density was 4 g/L. Over-liming treatment of crude pyrolytic acetic acid increased the algal growth with a concurrent reduction of cell membrane leakage. Directed evolution of algal strain enhanced cell membrane integrity and thus increased its tolerance to the toxicity of the crude substrate. Statistical analysis shows that there was a significant correlation between the cell growth performance and the cell membrane integrity (leakage) but not membrane fluidity. The addition of cyto-protectants such as Pluronic F68 and Pluronic F127 enhanced the cell membrane integrity and thus, resulted in enhanced cell growth. The transmission electron microscopy (TEM) of algal cells visually confirmed the cell membrane damage as the mechanism of the pyrolytic substrate inhibition. Collectively, this work indicates that the cell membrane is one major reason for the toxicity of pyrolytic acetic acid when being used for algal culture. To better use this pyrolytic substrate, cell membrane of the microorganism needs to be strengthened through either strain improvement or addition of membrane protectant reagents. [ABSTRACT FROM AUTHOR]

Approximately 100 million tons of anhydrosugars, such as levoglucosan and cellobiosan, are produced through biomass burning every year. These sugars are also produced through fast pyrolysis, the controlled thermal depolymerization of biomass. While the microbial pathways associated with levoglucosan utilization have been characterized, there is little known about cellobiosan utilization. Here we describe the isolation and characterization of six cellobiosan-utilizing microbes from soil samples. Each of these organisms is capable of using both cellobiosan and levoglucosan as sole carbon source, though both minimal and rich media cellobiosan supported significantly higher biomass production than levoglucosan. Ribosomal sequencing was used to identify the closest reported match for these organisms: Sphingobacterium multivorum, Acinetobacter oleivorans JC3-1, Enterobacter sp SJZ-6, and Microbacterium sps FXJ8.207 and 203 and a fungal species Cryptococcus sp. The commercially-acquired Enterobacter cloacae DSM 16657 showed growth on levoglucosan and cellobiosan, supporting our isolate identification. Analysis of an existing database of 16S rRNA amplicons from Iowa soil samples confirmed the representation of our five bacterial isolates and four previously-reported levoglucosan-utilizing bacterial isolates in other soil samples and provided insight into their population distributions. Phylogenetic analysis of the 16S rRNA and 18S rRNA of strains previously reported to utilize levoglucosan and our newfound isolates showed that the organisms isolated in this study are distinct from previously described anhydrosugar-utilizing microbial species. [ABSTRACT FROM AUTHOR]

Bio-oil derived from fast pyrolysis of lignocellulosic biomass contains various substrates that can be fermented to fuels and chemicals. The goal of this research was to utilize an acetic acid-rich fraction of bio-oil for the growth and lipid production by microalga Chlamydomonas reinhardtii. As toxic compounds are contained in the bio-oil, the algae cannot survive in medium containing this bio-oil fraction even at a low level (0.05 wt %). An alkali-based treatment with sodium hydroxide was used to reduce the toxicity and enhance its fermentability by microalgae. It was found that treating the acetic acid-rich bio-oil fraction by adjusting pH to 10 greatly improved the algal growth. The algae can thrive in medium containing 4 wt % alkali-treated bio-oil fraction. When using a metabolic-evolved strain with high level of toxicity tolerance, the algae were even capable of growing in medium containing 5.5 wt % bio-oil fraction, which replaced 100% of the acetic acid in the medium. The algal biomass grown in medium containing alkali-treated bio-oil fraction exhibited fatty acid profiles similar to the culture grown in pure acetic acid, but with a lower total fatty acid content. but the total fatty acid content (∼10% DW) was lower than that of the control (∼20% DW).The benefit of alkali treatment for enhancing algal growth was confirmed to be due to the removal of toxic compounds such as furfural, acetol, phenolics, and 5-hydroxymethylfurfural (HMF). Collectively, the results showed that fast pyrolysis-microalgal fermentation is a viable approach for producing lipid from lignocellulosic biomass. Alkali-based treatment is an effective method for reducing bio-oil toxicity, and thereby, greatly enhancing the algae fermentability of bio-oil. © 2013 American Institute of Chemical Engineers Environ Prog, 32: 955-961, 2013 [ABSTRACT FROM AUTHOR]

Abstract Thermochemical processing is a promising method for the rapid depolymerization of biomass. This study investigated switchgrass, corn stover, red oak, hybrid poplar, and loblolly pine in terms of heteropolymer and elemental composition, and the distribution and composition of the fast pyrolysis products. Corn stover differed from other biomass types in that less of the biomass was recovered as sugar or phenolic oil (PO) and more of the biomass was recovered as bio-char and bio-gas. The sugar-rich aqueous stream recovered from the bio-oil heavy fraction was characterized in terms of sugar content and distribution, inhibitor content, and ability to support production of ethanol by Escherichia coli KO11 + lgk as a model biorenewable product. Levoglucosan was the most abundant sugar from each type of biomass, followed by either xylose or cellobiosan. For hybrid poplar, cellobiosan accounted for 30 wt% of the total sugar pool. Each of the sugar streams also contained a variety of inhibitors, particularly 5-hydroxymethylfurfural (5-HMF) and methylcyclopentenolone. Methylcyclopentenolone, maple lactone, was found to decrease the specific growth rate of E. coli by 50% when present at 0.72 wt%, indicating that it is less toxic than furfural, acetic acid and guaiacol. Sugars produced from switchgrass contained 4-fold less contaminants on a per-sugar basis than those from poplar and pine. All of the sugar streams contained too many inhibitors to be used at an industrially feasible concentration without additional detoxification. The poplar-derived pyrolytic sugar syrup was particularly inhibitory, possibly due to the high abundance of aromatic hydrocarbons, such as xylenes, and anisoles. Highlights • Corn stover pyrolysis produced less sugar or phenolic oil than other biomass types. • Maple lactone is abundant in pyrolytic sugars, but its toxicity to E. coli is low. • Sugar syrup derived from poplar showed high toxicity to ethanologenic E. coli. • Xylene and anisole content trends with observed toxicity of sugar stream. • Anhydrosugar distribution differs between biomass types. [ABSTRACT FROM AUTHOR]

Thermochemical–biological hybrid processing uses thermochemical decomposition of lignocellulosic biomass to produce a variety of intermediate compounds that can be converted into fuels and chemicals through microbial fermentation. It represents a unique opportunity for biomass conversion as it mitigates some of the deficiencies of conventional biochemical (pretreatment–hydrolysis–fermentation) and thermochemical (pyrolysis or gasification) processing. Thermochemical–biological hybrid processing includes two pathways: (i) pyrolysis/pyrolytic substrate fermentation, and (ii) gasification/syngas fermentation. This paper provides a comprehensive review of these two hybrid processing pathways, including the characteristics of fermentative substrates produced in the thermochemical stage and microbial utilization of these compounds in the fermentation stage. The current challenges of these two biomass conversion pathways include toxicity of the crude pyrolytic substrates, the inhibition of raw syngas contaminants, and the mass-transfer limitations in syngas fermentation. Possible approaches for mitigating substrate toxicities are discussed. The review also provides a summary of the current efforts to commercialize hybrid processing. [ABSTRACT FROM AUTHOR]

Bio-oil derived from Pyrolysis of lignocellulosic biomass contains appreciable amounts acetic acid, which can be used as substrate for growing microalgae Chlamydomonas reinhardtii . However, the toxic compounds in the bio-oil inhibit the cell growth. This work is to develop alkaline treatment methods to reduce the toxicity and improve fermentability of acetic acid rich bio-oil. When growing in raw bio-oil without any detoxification treatment, the algae can only tolerate up to 0.1 wt% of bio-oil. Treatment with KOH, NaOH and Ca(OH) 2 significantly reduced the toxicity and consequently improved the fermentability of bio-oil. The bio-oil tolerant level by microalgae depended on the alkali species used. Among the three alkali species, Ca(OH) 2 proved the most effective detoxification reagent. Inhibitory compounds such as furans, phenols, ketones, aldehydes, ethers, esters, alcohols were removed by Ca(OH) 2 treatment through precipitation. The detoxification mechanisms by the Ca(OH) 2 -based treatment were also explored. The synergistic effect of alkaline pH, high temperature, and presence of Ca 2+ played an important role for the precipitation of those compounds, and the consequent detoxification. Collectively, the results shows alkali, particularly Ca(OH) 2 -based, treatment is an effective for reducing the toxicity of the pyrolysis derived bio-oil as fermentative substrate for microalgae growth. The microalgae can tolerant Ca(OH) 2 -treated bio-oil up to 5.5 wt%, which was 55 times higher than algal tolerance level of untreated bio-oil. [ABSTRACT FROM AUTHOR]

Abstract: This work was to utilize acetic acid contained in bio-oil for growth and lipid production of the microalga Chlamydomonas reinhardtii. The acetic acid-rich bio-oil fraction derived from fast pyrolysis of softwood contained 26% (w/w) acetic acid, formic acid, methanol, furfural, acetol, and phenolics as identified compounds, and 13% (w/w) unidentified compounds. Among those identified compounds, phenolics were most inhibitory to algal growth, followed by furfural and acetol. To enhance the fermentability of the bio-oil fraction, activated carbon was used to reduce the toxicity of the bio-oil, while metabolic evolution was used to enhance the toxicity tolerance of the microalgae. Combining activated carbon treatment and using evolved algal strain resulted in significant algal growth improvement. The results collectively showed that fast pyrolysis-fermentation process was a viable approach for converting biomass into fuels and chemicals. [Copyright &y& Elsevier]