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The use of microorganisms is a promising option for an eco-efficient and successful conversion of hardwood hemicelluloses to biofuels. The focus of this work is the treatment of hemicellulosic pre-hydrolysate by flocculation, followed by simultaneous or separate detoxification with Ureibacillus thermosphaericus and Cupriavidus taiwanensis co-culture, and hydrolysis with Paenibacillus campinasensis. A reduction of phenolic compounds was achieved mainly after flocculation, applied as a first detoxification step, but no increase in sugars concentration was observed. The ABE fermentation of the hydrolysate obtained from the simultaneous hydrolysis and detoxification produced 6.8 g L -1 of butanol after 116 h, which was higher than that generated with xylose synthetic medium. The higher biofuel concentration in the hydrolysate is attributed to the existence of carbon sources, other than xylose., (Crown Copyright © 2019. Published by Elsevier Inc. All rights reserved.)

Kraft prehydrolysate contains fermentable sugars and other organic compounds such as furans, phenolic compounds and acids, which are toxic to the fermentation microorganisms. In this work, bacteria-derived laccases were used to degrade key phenolic compounds. Firstly, the potential of degrading the key phenolic compounds in the prehydrolysate was determined. This was followed by tests with synthetic solutions to determine how specific phenolic compounds, vanillin, gallic acid, catechol and syringaldehyde, are degraded individually and in synergy. An evaluation of the simultaneous detoxification and enzymatic hydrolysis of the sugars was performed. The results showed that an enzyme dosage of at least 100 µL of laccase/g of phenol is required to obtain a significant detoxification of the prehydrolysate. Differences in the degradation of the compounds in single-component solutions and in a mixture were identified. Gallic acid and syringaldehyde are preferentially degraded, followed by vanillin and catechol. [ABSTRACT FROM AUTHOR]

In this study, a new fermentation medium combining a flocculated hemicellulosic wood hydrolysate (FHWH), rich in carbohydrates, obtained from a pulp and paper mill and an alfalfa juice, rich in nitrogen was used to produce butanol by Clostridium acetobutylicum ATCC 842. It was demonstrated that pH control enhances solvent production. The culture containing the two renewable biomass resources resulted in the production of 3.80 g/L of acetone-butanol-ethanol (ABE) with a productivity of 0.03 g/L h and a yield of 0.14 g/g. The obtained results demonstrated that the proposed combination can be used as a new fermentation medium for ABE production. However, the complexity of the medium induced an inhibitory effect and a decrease in the production of ABE, compared to the fermentation of FHWH and yeast extract. [ABSTRACT FROM AUTHOR]

Butanol, a fuel with better characteristics than ethanol, can be produced via acetone–butanol–ethanol (ABE) fermentation using lignocellulosic biomass as a carbon source. However, many inhibitors present in the hydrolysate limit the yield of the fermentation process. In this work, a detoxification technology combining flocculation and biodetoxification within a bacterial co‐culture composed of Ureibacillus thermosphaericus and Cupriavidus taiwanensis is presented for the first time. Co‐culture‐based strategies to detoxify filtered and unfiltered hydrolysates have been investigated. The best results of detoxification were obtained for a two‐step approach combining flocculation to biodetoxification. This sequential process led to a final phenolic compounds concentration of 1.4 g/L, a value close to the minimum inhibitory level observed for flocculated hydrolysate (1.1 g/L). The generated hydrolysate was then fermented with Clostridium acetobutylicum ATCC 824 for 120 h. A final butanol production of 8 g/L was obtained, although the detoxified hydrolysate was diluted to reach 0.3 g/L of phenolics to ensure noninhibitory conditions. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 35: e2753, 2019. [ABSTRACT FROM AUTHOR]

Theprehydrolysate stream from a Kraft dissolving pulp mill canbe valorized by fermentation of the hemicellulosic sugars into biofuelsor bioproducts, such as ethanol or butanol, instead of the typicalpractice of combustion to produce energy. An obstacle facing the useof Kraft hemicelluloses prehydrolysate for biofuels production isthe low sugar concentration and the presence of fermentation inhibitorsthat include organic acids, furans and phenolic compounds. A preconditionto ensure the survival of the fermentation microorganisms and to havehigh fermentation yields is to remove the inhibitors. Concentrationof the prehydrolysate is also necessary to reduce the size of theprocessing equipment and decrease the energy cost. The purpose ofthis study was to develop a strategy for the concentration and detoxificationof hemicelluloses prehydrolysate prior to its conversion into biofuels.Experiments were conducted to screen and select suitable organic membranesamong 7 samples of reverse osmosis, nanofiltration, and ultrafiltrationmembranes. Three membranes (Dow NF270, Trisep TS40, and Trisep XN45)showed the highest sugar retentions relative to inhibitors removal.They were however not efficient for the removal of the phenolic compounds.It was also found that flocculation with ferric sulfate as coagulantcould be utilized as a secondary detoxification step that can be combinedwith nanofiltration. The optimization of the flocculation step witha jar test showed that the highest phenolics removal (∼80%)can be obtained when the ratio of ferric ions to phenols is 1 g/g,and the pH is between 6.5 and 7.5. A new process concept for the detoxificationand concentration has been developed based on these experimental results. [ABSTRACT FROM AUTHOR]