Development of yeast cell factories for consolidated bioprocessing of lignocellulose to bioethanol through cell surface engineering

Recently, lignocellulosic biomass as the most abundant renewable resource has been widely considered for bioalcohols production However, the complex structure of lignocelluloses requires a multi-step process which is costly and time consuming Although, several bioprocessing approaches have been developed for pretreatment, saccharification and fermentation, bioalcohols production from lignocelluloses is still limited because of the economic infeasibility of these technologies This cost constraint could be overcome by designing and constructing robust cellulolytic and bioalcohols producing microbes and by using them in a consolidated bioprocessing (CBP) system This paper comprehensively reviews potentials, recent advances and challenges faced in CBP systems for efficient bioalcohols (ethanol and butanol) production from lignocellulosic and starchy biomass The CBP strategies include using native single strains with cellulytic and alcohol production activities, microbial co-cultures containing both cellulytic and ethanologenic microorganisms, and genetic engineering of cellulytic microorganisms to be alcohol-producing or alcohol producing microorganisms to be cellulytic Moreover, high-throughput techniques, such as metagenomics, metatranscriptomics, next generation sequencing and synthetic biology developed to explore novel microorganisms and powerful enzymes with high activity, thermostability and pH stability are also discussed Currently, the CBP technology is in its infant stage, and ideal microorganisms and/or conditions at industrial scale are yet to be introduced So, it is essential to bring into attention all barriers faced and take advantage of all the experiences gained to achieve a high-yield and low-cost CBP process

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Advances in consolidated bioprocessing systems for bioethanol and butanol production from biomass: a comprehensive review

Next generation biofuel engineering in prokaryotes

Zymomonas mobilis is a natural ethanologen with many desirable industrial biocatalyst characteristics. In this review, we will discuss work to develop Z. mobilis as a model system for biofuel production from the perspectives of substrate utilization, development for industrial robustness, potential product spectrum, strain evaluation and fermentation strategies. This review also encompasses perspectives related to classical genetic tools and emerging technologies in this context.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/1751-7915.12408

Zymomonas mobilis as a model system for production of biofuels and biochemicals

Endowing non-cellulolytic microorganisms with cellulolytic activity aiming for consolidated bioprocessing

Cellulosic ethanol production by Zymomonas mobilis harboring an endoglucanase gene from Enterobacter cloacae.

Carbon (neutral) based renewable liquid biofuels are alternative to petroleum derived transport fuels that contribute to global warming and are of a limited availability. Microalgae based biofuels are considered as promising source of energy. Lyngbya sp. and Synechococcus sp. were studied for the possibility of biodiesel production in different media such as ASNIII, sea water enrichment medium and BG11. The sea water enrichment medium was found superior in enhancing the growth rate of these microalgae. Nitrogen depletion has less effect in total chlorophyll a content, at the same time the lipid content was increased in both Lyngbya sp. and Synechococcus sp. by 1.4 and 1.2 % respectively. Increase in salinity from 0.5-1.0 M also showed an increase in the lipid content to 2.0 and 0.8 % in these strains; but a salinity of 1.5 M has a total inhibitory effect in the growth. The total biomass yield was comparatively higher in tubular LED photobioreactor than the fluorescent flat plated photobioreactor. Lipid extraction was obtained maximum at 60 degrees C in 1:10 sample: solvent ratio. GC-MS analysis of biodiesel showed high content of polyunsaturated fatty acids (PUFA; 4.86 %) than saturated fatty acid (SFA; 4.10 %). Biodiesel production was found maximum in Synechococcus sp. than Lyngbya sp. The viscosity of the biodiesel was closely related to conventional diesel. The results strongly suggest that marine microalgae could be used as a renewable energy source for biodiesel production.

http://nopr.niscair.res.in/bitstream/123456789/16129/1/IJEB%2051%283%29%20262-268.pdf

Biodiesel production from marine cyanobacteria cultured in plate and tubular photobioreactors.

The ethanol fermenting genes such as pyruvate decarboxylase (pdc) and alcohol dehydrogenase II (adh II) were cloned from Zymomonas mobilis and transformed into three different cellulolytic bacteria, namely Enterobacter cloacae JV, Proteus mirabilis JV and Erwinia chrysanthemi and their cellulosic ethanol production capability was studied. Recombinant E. cloacae JV was found to produce 4.5% and 3.5% (v/v) ethanol, respectively, when CMC and 4% NaOH pretreated bagasse were used as substrates, whereas recombinant P. mirabilis and E. chrysanthemi with the same substrates could only produce 4%, 3.5%, 1%, and 1.5 % of ethanol, respectively. The recombinant E. cloacae strain produced twofold higher percentage of ethanol than the wild type. The recombinant E. cloacae strain could be improved further by increasing its ethanol tolerance capability through media optimization and also by combining multigene cellulase expression for enhancing ethanol production from various types of lignocellulosic biomass so that it can be used for industrial level ethanol production.

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Cellulosic Ethanol Production by Recombinant Cellulolytic Bacteria Harbouring pdc and adh II Genes of Zymomonas mobilis.

Molecular characterization of mosquitocidal Bacillus sphaericus isolated from Tamil Nadu, India.

The yeast strains Schizosaccharomyces pombe and Saccharomyces cerevisiae are known best for their ethanol production capability at the industrial level which produces about 12% of ethanol from glucose through fermentation process. The substrate utilization of these strains is limited and so it fails to utilize cellulose. As an attempt to produce cellulosic ethanol from S. pombe and S. cerevisiae from pretreated lignocellulosic biomass which was hydrolyzed separately with crude cellulase system of E. cloacae JV and B. licheniformis for the conversion of cellulose to glucose. Then the fermentation was carried out with the glucose present in the hydrolysate as substrate. The ethanol produced by S. pombe and S. cerevisiae from microbial hydrolysis of 4% NaOH treated rice straw was 7 % and 7-9% respectively.

P. Sobana Piriya

Papers

Cellulosic ethanol production by Zymomonas mobilis harboring an endoglucanase gene from Enterobacter cloacae.

Biodiesel production from marine cyanobacteria cultured in plate and tubular photobioreactors.

Cellulosic Ethanol Production by Recombinant Cellulolytic Bacteria Harbouring pdc and adh II Genes of Zymomonas mobilis.

Molecular characterization of mosquitocidal Bacillus sphaericus isolated from Tamil Nadu, India.

Comparison of cellulosic ethanol production of schizosaccharomyces pombe and saccharomyces cerevisiae from glucose hydrolysate