Boosting Ethanol Productivity of Zymomonas mobilis 8b in Enzymatic Hydrolysate of Dilute Acid and Ammonia Pretreated Corn Stover Through Medium Optimization, High Cell Density Fermentation and Cell Recycling

Li, Ying; Zhai, Rui; Jiang, Xiaoxiao; Chen, Xiangxue; Yuan, Xinchuan; Liu, Zhihua; Jin, Mingjie

doi:10.3389/fmicb.2019.02316

Cited by 23 publications

(14 citation statements)

References 40 publications

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“…Compared with the fermentation under 50 g/L xylose and 100 g/L xylose, the xylose consumption and ethanol production were decreased in all three strains under 150 g/L xylose. This phenomenon was consistent with previous works that the higher the xylose concentration is, the more difficult it is for cells to complete fermentation [ 12 , 16 , 39 ]. It can be attributed to the production of ethanol and toxic intermediates derived from xylose such as xylitol and xylonate [ 31 , 40 ].…”

Section: Resultssupporting

confidence: 93%

“…The result suggested that sugar sources had a great effect on cell growth, and glucose was superior to xylose as the carbon source for ethanol fermentation. The slower consumption of xylose and less energy generation for cell growth may be the main reason for slower xylose metabolism as reported before [ 39 ]. As depicted, all strains could consume 50 g/L glucose completely to get a maximum OD 600 around 5.20 and ethanol titer around 25 g/L (Fig.…”

Section: Resultsmentioning

confidence: 62%

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Development and characterization of efficient xylose utilization strains of Zymomonas mobilis

Lou

Wang

Yang

et al. 2021

Biotechnol Biofuels

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Background Efficient use of glucose and xylose is a key for the economic production of lignocellulosic biofuels and biochemicals, and different recombinant strains have been constructed for xylose utilization including those using Zymomonas mobilis as the host. However, the xylose utilization efficiency still needs to be improved. In this work, the strategy of combining metabolic engineering and adaptive laboratory evolution (ALE) was employed to develop recombinant Z. mobilis strains that can utilize xylose efficiently at high concentrations, and NGS-based genome resequencing and RNA-Seq transcriptomics were performed for strains evolved after serial transfers in different media to understand the impact of xylose and differences among strains with different xylose-utilization capabilities at molecular level. Results Heterologous genes encoding xylose isomerase and xylulokinase were evaluated, which were then introduced into xylose-utilizing strain Z. mobilis 8b to enhance its capacity of xylose utilization. The results demonstrated that the effect of three xylose isomerases on xylose utilization was different, and the increase of copy number of xylose metabolism genes can improve xylose utilization. Among various recombinant strains constructed, the xylose utilization capacity of the recombinant strain 8b-RsXI-xylB was the best, which was further improved through continuous adaption with 38 transfers over 100 days in 50 g/L xylose media. The fermentation performances of the parental strain 8b, the evolved 8b-S38 strain with the best xylose utilization capability, and the intermediate strain 8b-S8 in different media were compared, and the results showed that only 8b-S38 could completely consume xylose at 50 g/L and 100 g/L concentrations. In addition, the xylose consumption rate of 8b-S38 was faster than that of 8b at different xylose concentrations from 50 to 150 g/L, and the ethanol yield increased by 16 ~ 40%, respectively. The results of the mixed-sugar fermentation also demonstrated that 8b-S38 had a higher xylose consumption rate than 8b, and its maximum ethanol productivity was 1.2 ~ 1.4 times higher than that of 8b and 8b-S8. Whole-genome resequencing identified three common genetic changes in 8b-S38 compared with 8b and 8b-S8. RNA-Seq study demonstrated that the expression levels of genes encoding chaperone proteins, ATP-dependent proteases, phage shock proteins, ribosomal proteins, flagellar operons, and transcriptional regulators were significantly increased in xylose media in 8b-S38. The up-regulated expression of these genes may therefore contribute to the efficient xylose utilization of 8b-S38 by maintaining the normal cell metabolism and growth, repairing cellular damages, and rebalancing cellular energy to help cells resist the stressful environment. Conclusions This study provides gene candidates to improve xylose utilization, and the result of expressing an extra copy of xylose isomerase and xylulokinase improved xylose utilization also provides a direction for efficient xylose-utilization strain development in other microorganisms. In addition, this study demonstrated the necessity to combine metabolic engineering and ALE for industrial strain development. The recombinant strain 8b-S38 can efficiently metabolize xylose for ethanol fermentation at high xylose concentrations as well as in mixed sugars of glucose and xylose, which could be further developed as the microbial biocatalyst for the production of lignocellulosic biofuels and biochemicals.

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Section: Resultssupporting

confidence: 93%

Section: Resultsmentioning

confidence: 62%

Development and characterization of efficient xylose utilization strains of Zymomonas mobilis

Lou

Wang

Yang

et al. 2021

Biotechnol Biofuels

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“…57 For example, a self-flocculating H. campaniensis LS21 strain has been successfully constructed for wastewater- less PHB fermentation, 58 and a previous study also demonstrated that high cell density fermentation with cell recycling in Z. mobilis 8b can improve the ethanol titer and metabolic yield in a lignocellulosic hydrolysate. 59 Therefore, it is feasible to deploy the cell recycling in the recombinant PHB-producing Z. mobilis strain to produce PHB and ethanol simultaneously.…”

Section: Continuous Co-production Of Ethanol and Phbmentioning

confidence: 99%

Metabolic engineering ofZymomonas mobilisfor continuous co-production of bioethanol and poly-3-hydroxybutyrate (PHB)

Yang

Wang

et al. 2022

Green Chem.

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“…Zymomonas mobilis is an ethanol-tolerant bacterium that ferments a wide variety of monosaccharides and produces bioethanol in significant quantities ( Kurumbang et al, 2019 ). It possesses some unique properties that make it an excellent candidate to be considered as a substitute for yeast in the manufacturing of bioethanol ( Li et al, 2019 ). Utilizing this bacterium as an expression platform for recombinant protein shows about 12–30 times higher protein expression when compared to E. coli ( Kurumbang et al, 2019 ).…”

Section: Expression Of Thermostable Cellulase and Xylanasementioning

confidence: 99%

Thermostable Cellulases / Xylanases From Thermophilic and Hyperthermophilic Microorganisms: Current Perspective

Ajeje¹,

Hu²,

Song³

et al. 2021

Front. Bioeng. Biotechnol.

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The bioconversion of lignocellulose into monosaccharides is critical for ensuring the continual manufacturing of biofuels and value-added bioproducts. Enzymatic degradation, which has a high yield, low energy consumption, and enhanced selectivity, could be the most efficient and environmentally friendly technique for converting complex lignocellulose polymers to fermentable monosaccharides, and it is expected to make cellulases and xylanases the most demanded industrial enzymes. The widespread nature of thermophilic microorganisms allows them to proliferate on a variety of substrates and release substantial quantities of cellulases and xylanases, which makes them a great source of thermostable enzymes. The most significant breakthrough of lignocellulolytic enzymes lies in lignocellulose-deconstruction by enzymatic depolymerization of holocellulose into simple monosaccharides. However, commercially valuable thermostable cellulases and xylanases are challenging to produce in high enough quantities. Thus, the present review aims at giving an overview of the most recent thermostable cellulases and xylanases isolated from thermophilic and hyperthermophilic microbes. The emphasis is on recent advancements in manufacturing these enzymes in other mesophilic host and enhancement of catalytic activity as well as thermostability of thermophilic cellulases and xylanases, using genetic engineering as a promising and efficient technology for its economic production. Additionally, the biotechnological applications of thermostable cellulases and xylanases of thermophiles were also discussed.

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Boosting Ethanol Productivity of Zymomonas mobilis 8b in Enzymatic Hydrolysate of Dilute Acid and Ammonia Pretreated Corn Stover Through Medium Optimization, High Cell Density Fermentation and Cell Recycling

Cited by 23 publications

References 40 publications

Development and characterization of efficient xylose utilization strains of Zymomonas mobilis

Development and characterization of efficient xylose utilization strains of Zymomonas mobilis

Metabolic engineering ofZymomonas mobilisfor continuous co-production of bioethanol and poly-3-hydroxybutyrate (PHB)

Thermostable Cellulases / Xylanases From Thermophilic and Hyperthermophilic Microorganisms: Current Perspective

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