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Wu R.,Guangxi University for Nationalities | Zhao X.,Tsinghua University | Zhao X.,Tsinghua Innovation Center in Dongguan | Liu D.,Tsinghua University | Liu D.,Tsinghua Innovation Center in Dongguan
ACS Sustainable Chemistry and Engineering | Year: 2016

Enzymatic digestibility of sugar cane bagasse could be greatly enhanced by Formiline pretreatment, which comprises a formic acid (FA) delignification followed by an alkaline deformylation. The FA can be easily recovered and recycled for delignification, indicating that this pretreatment is a green process for biomass fractionation. It was found that removing hemicelluloses and lignin during pretreatment contributed to the increase of cellulose accessibility; however, delignification seemed to be more important for exposing cellulose fibers. The compact cell wall structure of raw bagasse was destroyed by removing considerable parts of lignin and hemicelluloses with liberation of cellulose fibers, and the specific surface area of the pretreated substrates increased by more than 2-fold. However, formylation of cellulose took place during FA delignification, which showed significant negative impact on the initial enzymatic hydrolysis rate and enzymatic polysaccharide conversion at 120 h. Removing formyl groups by alkaline post-treatment could well recover the cellulose digestibility but without significant alteration of the substrate structure. © 2016 American Chemical Society.

Chen Z.,Tsinghua University | Chen Z.,Tsinghua Innovation Center in Dongguan | Sun H.,Tsinghua University | Huang J.,Tsinghua University | And 3 more authors.
PLoS ONE | Year: 2015

2-Butanone is an important commodity chemical of wide application in different areas. In this study, Klebsiella pneumoniae was engineered to directly produce 2-butanone from glucose by extending its native 2, 3-butanediol synthesis pathway. To identify the potential enzyme for the efficient conversion of 2, 3-butanediol to 2-butanone, we screened different glycerol dehydratases and diol dehydratases. By introducing the diol dehydratase from Lactobacillus brevis and deleting the ldhA gene encoding lactate dehydrogenase, the engineered K. pneumoniae was able to accumulate 246 mg/L of 2-butanone in shake flask. With further optimization of culture condition, the titer of 2-butanone was increased to 450 mg/L. This study lays the basis for developing an efficient biological process for 2-butanone production. © Copyright: 2015 Chen et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Akimkulova A.,Tsinghua University | Zhou Y.,Tsinghua University | Zhao X.,Tsinghua University | Zhao X.,Tsinghua Innovation Center in Dongguan | And 2 more authors.
Bioresource Technology | Year: 2016

Eleven salts were selected to screen the possible metal ions for blocking the non-productive adsorption of cellulase onto the lignin of dilute acid pretreated wheat straw. Mg2+ was screened finally as the promising candidate. The optimal concentration of MgCl2 was 1 mM, but the beneficial action was also dependent on pH, hydrolysis time and cellulase loading. Significant improvement of glucan conversion (19.3%) was observed at low cellulase loading (5 FPU/g solid). Addition of isolated lignins, tannic acid and lignin model compounds to pure cellulose hydrolysis demonstrated that phenolic hydroxyl group (Ph-OH) was the main active site blocked by Mg2+. The interaction between Mg2+ and Ph-OH of lignin monomeric moieties followed an order of p-hydroxyphenyl (H) > guaiacyl (G) > syringyl (S). Mg2+ blocking made the lignin surface less negatively charged, which might weaken the hydrogen bonding and electrostatically attractive interaction between lignin and cellulase enzymes. © 2016 Elsevier Ltd.

Chen Z.,Tsinghua University | Chen Z.,Tsinghua Innovation Center in Dongguan | Huang J.,Tsinghua University | Wu Y.,Tsinghua University | And 2 more authors.
Metabolic Engineering | Year: 2016

Development of sustainable biological process for the production of bulk chemicals from renewable feedstock is an important goal of white biotechnology. Ethylene glycol (EG) is a large-volume commodity chemical with an annual production of over 20. million. tons, and it is currently produced exclusively by petrochemical route. Herein, we report a novel biosynthetic route to produce EG from glucose by the extension of serine synthesis pathway of Corynebacterium glutamicum. The EG synthesis is achieved by the reduction of glycoaldehyde derived from serine. The transformation of serine to glycoaldehyde is catalyzed either by the sequential enzymatic deamination and decarboxylation or by the enzymatic decarboxylation and oxidation. We screened the corresponding enzymes and optimized the production strain by combinatorial optimization and metabolic engineering. The best engineered C. glutamicum strain is able to accumulate 3.5. g/L of EG with the yield of 0.25. mol/mol glucose in batch cultivation. This study lays the basis for developing an efficient biological process for EG production. © 2015 International Metabolic Engineering Society.

Tian X.,Tsinghua University | Dai L.,Tsinghua University | Liu M.,ENN Group | Liu D.,Tsinghua University | And 4 more authors.
Catalysis Communications | Year: 2016

A novel process with the combined use of lipase NS81006 and Novozym435 was developed for the conversion of microalgae oils for biodiesel production and PUFAs concentration. It was found that during the first-step reaction catalyzed by NS81006, the reaction rates of PUFAs were much slower compared to those with carbon length varying from C14 to C18, but significant increase for PUFAs' conversion was achieved with Novozym435 as the catalyst for the second step conversion. A fatty acid methyl ester (FAME) yield of 95% could be obtained with this two-step enzymatic catalysis. This process has great prospect for converting microalgae oils for biodiesel preparation and PUFAs concentration. © 2016 Elsevier B.V. All rights reserved.

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