Intracellular cellobiose metabolism and its applications in lignocellulose-based biorefineries

Parisutham, Vinuselvi,Chandran, Sathesh-Prabu,Mukhopadhyay, Aindrila,Lee, Sung Kuk,Keasling, Jay D. Elsevier Applied Science 2017 Bioresource technology Vol.239 No.-

<P><B>Abstract</B></P> <P>Complete hydrolysis of cellulose has been a key characteristic of biomass technology because of the limitation of industrial production hosts to use cellodextrin, the partial hydrolysis product of cellulose. Cellobiose, a <I>β</I>-1,4-linked glucose dimer, is a major cellodextrin of the enzymatic hydrolysis (via endoglucanase and exoglucanase) of cellulose. Conversion of cellobiose to glucose is executed by <I>β</I>-glucosidase. The complete extracellular hydrolysis of celluloses has several critical barriers in biomass technology. An alternative bioengineering strategy to make the bioprocessing less challenging is to engineer microbes with the abilities to hydrolyze and assimilate the cellulosic-hydrolysate cellodextrin. Microorganisms engineered to metabolize cellobiose rather than the monomeric glucose can provide several advantages for lignocellulose-based biorefineries. This review describes the recent advances and challenges in engineering efficient intracellular cellobiose metabolism in industrial hosts. This review also describes the limitations of and future prospectives in engineering intracellular cellobiose metabolism.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The complete hydrolysis of cellulose by cellulase cocktail poses several critical barriers. </LI> <LI> The intracellular cellobiose assimilation has been considered as an alternative strategy. </LI> <LI> Engineering the industrial hosts for efficient cellobiose utilization would be advantageous. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Rewiring carbon catabolite repression for microbial cell factory

( Parisutham Vinuselvi ),( Min Kyung Kim ),( Sung Kuk Lee ),( Cheol Min Ghim ) 생화학분자생물학회 (구 한국생화학분자생물학회) 2012 BMB Reports Vol.45 No.2

Carbon catabolite repression (CCR) is a key regulatory system found in most microorganisms that ensures preferential utilization of energy-efficient carbon sources. CCR helps microorganisms obtain a proper balance between their metabolic capacity and the maximum sugar uptake capability. It also constrains the deregulated utilization of a preferred cognate substrate, enabling microorganisms to survive and dominate in natural environments. On the other side of the same coin lies the tenacious bottleneck in microbial production of bioproducts that employs a combination of carbon sources in varied proportion, such as lignocellulose-derived sugar mixtures. Preferential sugar uptake combined with the transcriptional and/or enzymatic exclusion of less preferred sugars turns out one of the major barriers in increasing the yield and productivity of fermentation process. Accumulation of the unused substrate also complicates the downstream processes used to extract the desired product. To overcome this difficulty and to develop tailor-made strains for specific metabolic engineering goals, quantitative and systemic understanding of the molecular interaction map behind CCR is a prerequisite. Here we comparatively review the universal and strain-specific features of CCR circuitry and discuss the recent efforts in developing synthetic cell factories devoid of CCR particularly for lignocellulose- based biorefinery. [BMB reports 2012; 45(2): 59-70].

Engineering Escherichia coli for efficient cellobiose utilization

Vinuselvi, Parisutham,Lee, Sung Kuk Springer-Verlag 2011 Applied microbiology and biotechnology Vol.92 No.1

<P>Escherichia coli normally cannot utilize the beta-glucoside sugar cellobiose as a carbon and energy source unless a stringent selection pressure for survival is present. The cellobiose-utilization phenotype can be conferred by mutations in the two cryptic operons, chb and asc. In this study, the cellobiose-utilization phenotype was conferred to E. coli by replacing the cryptic promoters of these endogenous operons with a constitutive promoter. Evolutionary adaptation of the engineered strain CP12CHBASC by repeated subculture in cellobiose-containing minimal medium led to an increase in the rate of cellobiose uptake and cell growth on cellobiose. An efficient cellobiose-metabolizing E. coli strain would be of great importance over glucose-metabolizing E. coli for a simultaneous saccharification and fermentation process, as the cost of the process would be reduced by eliminating one of the three enzymes needed to hydrolyze cellulose into simple sugars.</P>

Microfluidic Technologies for Synthetic Biology

Vinuselvi, Parisutham,Park, Seongyong,Kim, Minseok,Park, Jung Min,Kim, Taesung,Lee, Sung Kuk Molecular Diversity Preservation International (MD 2011 INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES Vol.12 No.6

<P>Microfluidic technologies have shown powerful abilities for reducing cost, time, and labor, and at the same time, for increasing accuracy, throughput, and performance in the analysis of biological and biochemical samples compared with the conventional, macroscale instruments. Synthetic biology is an emerging field of biology and has drawn much attraction due to its potential to create novel, functional biological parts and systems for special purposes. Since it is believed that the development of synthetic biology can be accelerated through the use of microfluidic technology, in this review work we focus our discussion on the latest microfluidic technologies that can provide unprecedented means in synthetic biology for dynamic profiling of gene expression/regulation with high resolution, highly sensitive on-chip and off-chip detection of metabolites, and whole-cell analysis.</P>

Engineered <i>Escherichia coli</i> capable of co-utilization of cellobiose and xylose

Vinuselvi, Parisutham,Lee, Sung Kuk Elsevier 2012 Enzyme and microbial technology Vol.50 No.1

<P><B>Highlights</B></P><P>► This is the first strain of <I>E. coli</I> to efficiently co-utilize cellobiose and xylose for all ratios tested. ► This is a potentially important strain in simultaneous saccharification and co-fermentation process as it can utilize the major pentose and hexose derived from plant biomass simultaneously. ► This strain can be used for fermentation of both hardwood hydrolysate and softwood hydrolysate.</P> <P><B>Abstract</B></P><P>Natural ability to ferment the major sugars (glucose and xylose) of plant biomass is an advantageous feature of <I>Escherichia coli</I> in biofuel production. However, excess glucose completely inhibits xylose utilization in <I>E. coli</I> and decreases yield and productivity of fermentation due to sequential utilization of xylose after glucose. As an approach to overcome this drawback, <I>E. coli</I> MG1655 was engineered for simultaneous glucose (in the form of cellobiose) and xylose utilization by a combination of genetic and evolutionary engineering strategies. The recombinant <I>E. coli</I> was capable of utilizing approximately 6g/L of cellobiose and 2g/L of xylose in approximately 36h, whereas wild-type <I>E. coli</I> was unable to utilize xylose completely in the presence of 6g/L of glucose even after 75hours. The engineered strain also co-utilized cellobiose with mannose or galactose; however, it was unable to metabolize cellobiose in the presence of arabinose and glucose. Successful cellobiose and xylose co-fermentation is a vital step for simultaneous saccharification and co-fermentation process and a promising step towards consolidated bioprocessing.</P>

Heterologous Expression of Plant Cell Wall Degrading Enzymes for Effective Production of Cellulosic Biofuels

Jung, Sang-Kyu,Parisutham, Vinuselvi,Jeong, Seong Hun,Lee, Sung Kuk Hindawi Publishing Corporation 2012 Journal of biomedicine & biotechnology Vol.2012 No.-

<P>A major technical challenge in the cost-effective production of cellulosic biofuel is the need to lower the cost of plant cell wall degrading enzymes (PCDE), which is required for the production of sugars from biomass. Several competitive, low-cost technologies have been developed to produce PCDE in different host organisms such as <I>Escherichia coli, Zymomonas mobilis</I>, and plant. Selection of an ideal host organism is very important, because each host organism has its own unique features. Synthetic biology-aided tools enable heterologous expression of PCDE in recombinant <I>E. coli</I> or <I>Z. mobilis</I> and allow successful consolidated bioprocessing (CBP) in these microorganisms. <I>In-planta</I> expression provides an opportunity to simplify the process of enzyme production and plant biomass processing and leads to self-deconstruction of plant cell walls. Although the future of currently available technologies is difficult to predict, a complete and viable platform will most likely be available through the integration of the existing approaches with the development of breakthrough technologies.</P>