K T Shanmugam

University of Florida, Gainesville, Florida, United States

Are you K T Shanmugam?

Claim your profile

Publications (148)476.33 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: A techno-economic analysis was conducted for a simplified lignocellulosic ethanol production process developed and proven by the University of Florida at laboratory, pilot, and demonstration scales. Data obtained from all three scales of development were used with Aspen Plus to create models for an experimentally-proven base-case and 5 hypothetical scenarios. The model input parameters that differed among the hypothetical scenarios were fermentation time, enzyme loading, enzymatic conversion, solids loading, and overall process yield. The minimum ethanol selling price (MESP) varied between 50.38 and 62.72 US cents/L. The feedstock and the capital cost were the main contributors to the production cost, comprising between 23-28% and 40-49% of the MESP, respectively. A sensitivity analysis showed that overall ethanol yield had the greatest effect on the MESP. These findings suggest that future efforts to increase the economic feasibility of a cellulosic ethanol process should focus on optimization for highest ethanol yield.
    No preview · Article · Feb 2016 · Bioresource Technology
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In this study, a moderate thermophile Clostridium thermobutyricum is shown to ferment the sugars in sweet sorghum juice treated with invertase and supplemented with tryptone (10gL(-1)) and yeast extract (10gL(-1)) at 50°C to 44gL(-1) butyrate at a calculated highest volumetric productivity of 1.45gL(-1)h(-1) (molar butyrate yield of 0.85 based on sugars fermented). This volumetric productivity is among the highest reported for batch fermentations. Sugars from acid and enzyme-treated sweet sorghum bagasse were also fermented to butyrate by this organism with a molar yield of 0.81 (based on the amount of cellulose and hemicellulose). By combining the results from juice and bagasse, the calculated yield of butyric acid is approximately 90kg per tonne of fresh sweet sorghum stalk. This study demonstrates that C. thermobutyricum can be an effective microbial biocatalyst for production of bio-based butyrate from renewable feedstocks at 50°C.
    Full-text · Article · Sep 2015 · Bioresource Technology
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Sweet sorghum is a bioenergy crop that produces large amounts of soluble sugars in its stems (3–7 Mg ha−1) and generates significant amounts of bagasse (15–20 Mg ha−1) as a lignocellulosic feedstock. These sugars can be fermented not only to biofuels but also to bio-based chemicals. The market potential of the latter may be higher given the current prices of petroleum and natural gas. The yield and rate of production of optically pure d-(−)- and l-(+)-lactic acid as precursors for the biodegradable plastic polylactide was optimized for two thermotolerant Bacillus coagulans strains. Strain 36D1 fermented the sugars in unsterilized sweet sorghum juice at 50 °C to l-(+)-lactic acid (∼150 g L−1; productivity, 7.2 g L−1 h−1). B. coagulans strain QZ19-2 was used to ferment sorghum juice to d-(−)-lactic acid (∼125 g L−1; productivity, 5 g L−1 h−1). Carbohydrates in the sorghum bagasse were also fermented after pretreatment with 0.5 % phosphoric acid at 190 °C for 5 min. Simultaneous saccharification and co-fermentation of all the sugars (SScF) by B. coagulans resulted in a conversion of 80 % of available carbohydrates to optically pure lactic acid depending on the B. coagulans strain used as the microbial biocatalyst. Liquefaction of pretreated bagasse with cellulases before SScF (L + SScF) increased the productivity of lactic acid. These results show that B. coagulans is an effective biocatalyst for fermentation of all the sugars present in sweet sorghum juice and bagasse to optically pure lactic acid at high titer and productivity as feedstock for bio-based plastics.
    Full-text · Article · Aug 2015 · BioEnergy Research
  • [Show abstract] [Hide abstract]
    ABSTRACT: A bio-based process is appealing for purification of L-lactic acid, the major enantiomer of polylactic acid syrup, generated by thermochemical processes at the end of life of PLA-based plastics, from its chiral impurity, D-lactic acid, before reuse. Polylactic acid (PLA), a renewable alternative to petroleum-derived plastics, contains a mixture of L- and D-lactic acid (LA) isomers with the L-isomer dominating (up to 95 %). A novel bio-based process was developed to produce chirally pure L-LA from syrup produced during recycling of PLA-plastics. This process utilizes an engineered Escherichia coli (strain DC1001) containing novel gene deletions (lld, ykg) that eliminated the oxidative metabolism of L-lactate, leaving the membrane-bound D-lactate dehydrogenases to selectively metabolize the D-isomer. Strain DC1001 removed 8.7 g D-lactate l(-1) from a PLA-syrup containing 135 g total lactic acid l(-1) in 24 h. Average rates of removal of D-lactic acid were 0.25 g D-lactate h(-1) (g cell dry weight)(-1) and 0.36 g D-lactate l(-1) h(-1). Bio-based purification of PLA-syrup utilizing E. coli strain DC1001 is an attractive process step during recycling of PLA-plastics. This selective oxidation process can also be used to remove chiral contamination of L-lactate in medical applications.
    No preview · Article · Aug 2015 · Biotechnology Letters
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Escherichia coli KJ122 was engineered to produce succinate from glucose using the wild type GalP for glucose uptake instead of the native phosphotransferase system (ptsI mutation). This strain now ferments 10% xylose poorly. Mutants were selected by serial transfers in AM1 mineral salts medium with 10% xylose. Clones from this population all exhibited a similar improvement, co-fermentation of an equal mixture of xylose and glucose. One of these, AS1600a, produced 84.26 ± 1.37 g/L succinate, equivalent to that produced by the parent (KJ122) from 10% glucose (85.46 ± 1.78 g/L). AS1600a was sequenced and found to contain a mutation in galactose permease (GalP, G236D). This mutation was shown to be responsible for the improvement in fermentation using KJΔgalP as the host and expression vectors with native galP and with mutant galP∗. Strain AS1600a and KJΔgalP(pLOI5746; galP∗) also co-fermented a mixture of glucose, xylose, arabinose, and galactose in sugarcane bagasse hydrolysate using mineral salts medium.
    Full-text · Article · Jun 2015 · Bioresource Technology
  • Ryan Geddes · Keelnatham T Shanmugam · Lonnie O Ingram
    [Show abstract] [Hide abstract]
    ABSTRACT: Inhibitory side products from dilute acid pretreatment is a major challenge for conversion of lignocellulose into ethanol. Six strategies to detoxify sugarcane hydrolysates were investigated alone, and in combinations (vacuum evaporation of volatiles, high pH treatment with ammonia, laccase, bisulfite, microaeration, and inoculum size). High pH was the most beneficial single treatment, increasing the minimum inhibitory concentration (measured by ethanol production) from 15% (control) to 70% hydrolysate. Combining treatments provided incremental improvements, consistent with different modes of action and multiple inhibitory compounds. Screening toxicity using tube cultures proved to be an excellent predictor of relative performance in pH-controlled fermenters. A combination of treatments (vacuum evaporation, laccase, high pH, bisulfite, microaeration) completely eliminated all inhibitory activity present in hydrolysate. With this combination, fermentation of hemicellulose sugars (90% hydrolysate) to ethanol was complete within 48h, identical to the fermentation of laboratory xylose (50g/L) in AM1 mineral salts medium (without hydrolysate). Copyright © 2015 Elsevier Ltd. All rights reserved.
    No preview · Article · Mar 2015 · Bioresource Technology
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Expression of genes encoding polyamine transporters from plasmids and polyamine supplements increased furfural tolerance (growth and ethanol production) in ethanologenic Escherichia coli LY180 (AM1 mineral salts medium containing xylose). This represents a new approach to increase furfural tolerance and may be useful for other organisms. Microarray comparisons of two furfural-resistant mutants (EMFR9 and EMFR35) provided initial evidence for the importance of polyamine transporters. Each mutant contained a single polyamine transporter gene that was up regulated by over 100-fold (microarrays) compared to the parent LY180, and a mutation that silenced the expression of yqhD. Based on these genetic changes, furfural tolerance was substantially reconstructed in the parent LY180. Deletion of potE in EMFR9 lowered furfural tolerance to that of the parent. Deletion of potE and puuP in LY180 also decreased furfural tolerance, indicating functional importance of the native genes. Of the 8 polyamine transporters (18 genes) cloned and tested, half were beneficial for furfural tolerance (PotE, PuuP, PlaP and PotABCD). Supplementing AM1 mineral salts medium with individual polyamines (agmatine, putrescine and cadaverine) also increased furfural tolerance but to a smaller extent. In pH-controlled fermentations, polyamine transporter plasmids were shown to promote the metabolism of furfural and substantially reduce the time required to complete xylose fermentation. This increase in furfural tolerance is proposed to result from polyamine binding to negatively charged cellular constituents such as nucleic acids and phospholipids, providing protection from damage by furfural.
    Preview · Article · Jul 2014 · Applied and Environmental Microbiology
  • Source
    Huabao Zheng · Xuan Wang · Lorraine P Yomano · Ryan D Geddes · Keelnatham T Shanmugam · Lonnie O Ingram
    [Show abstract] [Hide abstract]
    ABSTRACT: Furfural is an inhibitory side product formed during the depolymerization of hemicellulose with mineral acids. In Escherichia coli, furfural tolerance can be increased by expressing the native fucO gene (encoding lactaldehyde oxidoreductase). This enzyme also catalyzes the NADH-dependent reduction of furfural to the less toxic alcohol. Saturation mutagenesis was combined with growth-based selection to isolate a mutated form of fucO that confers increased furfural tolerance. The mutation responsible, L7F, is located within the interfacial region of FucO homodimers, replacing the most abundant codon for leucine with the most abundant codon for phenylalanine. Plasmid expression of the mutant gene increased FucO activity by more than 10-fold compared to the wild-type fucO gene and doubled the rate of furfural metabolism during fermentation. No inclusion bodies were evident with either the native or the mutated gene. mRNA abundance for the wild-type and mutant fucO genes differed by less than 2-fold. The Km (furfural) for the mutant enzyme was 3-fold lower than that for the native enzyme, increasing efficiency at low substrate concentrations. The L7F mutation is located near the FucO N terminus, within the ribosomal binding region associated with translational initiation. Free-energy calculations for mRNA folding in this region (nucleotides −7 to +37) were weak for the native gene (−4.1 kcal mol−1) but weaker still for the fucO mutant (−1.0 to −0.1 kcal mol−1). The beneficial L7F mutation in FucO is proposed to increase furfural tolerance by improving gene expression and increasing enzyme effectiveness at low substrate levels.
    Full-text · Article · Mar 2013 · Applied and Environmental Microbiology
  • [Show abstract] [Hide abstract]
    ABSTRACT: Pretreatments such as dilute acid at elevated temperature are effective for the hydrolysis of pentose polymers in hemicellulose and also increase the access of enzymes to cellulose fibers. However, the fermentation of resulting syrups is hindered by minor reaction products such as furfural from pentose dehydration. To mitigate this problem, four genetic traits have been identified that increase furfural tolerance in ethanol-producing Escherichia coli LY180 (strain W derivative): increased expression of fucO, ucpA, or pntAB and deletion of yqhD. Plasmids and integrated strains were used to characterize epistatic interactions among traits and to identify the most effective combinations. Furfural resistance traits were subsequently integrated into the chromosome of LY180 to construct strain XW129 (LY180 ΔyqhD ackA::PfucO-ucpA) for ethanol. This same combination of traits was also constructed in succinate biocatalysts (Escherichia coli strain C derivatives) and found to increase furfural tolerance. Strains engineered for resistance to furfural were also more resistant to the mixture of inhibitors in hemicellulose hydrolysates, confirming the importance of furfural as an inhibitory component. With resistant biocatalysts, product yields (ethanol and succinate) from hemicellulose syrups were equal to control fermentations in laboratory media without inhibitors. The combination of genetic traits identified for the production of ethanol (strain W derivative) and succinate (strain C derivative) may prove useful for other renewable chemicals from lignocellulosic sugars.
    No preview · Article · Mar 2013 · Proceedings of the National Academy of Sciences
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A process was developed for seed culture expansion (3.6 million-fold) using 5% of the hemicellulose hydrolysate from dilute acid pretreatment as the sole organic nutrient and source of sugar. Hydrolysate used for seed growth was neutralized with ammonia and combined with 1.0mM sodium metabisulfite immediately before inoculation. This seed protocol was tested with phosphoric acid pretreated sugarcane and sweet sorghum bagasse using a simplified process with co-fermentation of fiber, pentoses, and hexoses in a single vessel (SScF). A 6h liquefaction (L) step improved mixing prior to inoculation. Fermentations (L+SScF process) were completed in 72h with high yields (>80gal/USton). Ethanol titers for this L+SScF process ranged from 24g/L to 32g/L, and were limited by the bagasse concentration (10% dry matter).
    Full-text · Article · Feb 2013 · Bioresource Technology
  • Source
    Huabao Zheng · Xuan Wang · Lorraine P Yomano · Keelnatham T Shanmugam · Lonnie O Ingram
    [Show abstract] [Hide abstract]
    ABSTRACT: Furfural is an inhibitory side product formed during the depolymerization of hemicellulose by mineral acids. Genomic libraries from three different bacteria (Bacillus subtilis YB886, Escherichia coli NC3, and Zymomonas mobilis CP4) were screened for genes that conferred furfural resistance on plates. Beneficial plasmids containing the thyA gene (coding for thymidylate synthase) were recovered from all three organisms. Expression of this key gene in the de novo pathway for dTMP biosynthesis improved furfural resistance on plates and during fermentation. A similar benefit was observed by supplementation with thymine, thymidine, or the combination of tetrahydrofolate and serine (precursors for 5,10-methylenetetrahydrofolate, the methyl donor for ThyA). Supplementation with deoxyuridine provided a small benefit, and deoxyribose was of no benefit for furfural tolerance. A combination of thymidine and plasmid expression of thyA was no more effective than either alone. Together, these results demonstrate that furfural tolerance is increased by approaches that increase the supply of pyrimidine deoxyribonucleotides. However, ThyA activity was not directly affected by the addition of furfural. Furfural has been previously shown to damage DNA in E. coli and to activate a cellular response to oxidative damage in yeast. The added burden of repairing furfural-damaged DNA in E. coli would be expected to increase the cellular requirement for dTMP. Increased expression of thyA (E. coli, B. subtilis, or Z. mobilis), supplementation of cultures with thymidine, and supplementation with precursors for 5,10-methylenetetrahydrofolate (methyl donor) are each proposed to increase furfural tolerance by increasing the availability of dTMP for DNA repair.
    Full-text · Article · Apr 2012 · Applied and Environmental Microbiology
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Pyruvate dehydrogenase (PDH) of Escherichia coli is inhibited by NADH. This inhibition is partially reversed by mutational alteration of the dihydrolipoamide dehydrogenase (LPD) component of the PDH complex (E354K or H322Y). Such a mutation in lpd led to a PDH complex that was functional in an anaerobic culture as seen by restoration of anaerobic growth of a pflB, ldhA double mutant of E. coli utilizing a PDH- and alcohol dehydrogenase-dependent homoethanol fermentation pathway. The glutamate at position 354 in LPD was systematically changed to all of the other natural amino acids to evaluate the physiological consequences. These amino acid replacements did not affect the PDH-dependent aerobic growth. With the exception of E354M, all changes also restored PDH-dependent anaerobic growth of and fermentation by an ldhA, pflB double mutant. The PDH complex with an LPD alteration E354G, E354P or E354W had an approximately 20-fold increase in the apparent K(i) for NADH compared with the native complex. The apparent K(m) for pyruvate or NAD(+) for the mutated forms of PDH was not significantly different from that of the native enzyme. A structural model of LPD suggests that the amino acid at position 354 could influence movement of NADH from its binding site to the surface. These results indicate that glutamate at position 354 plays a structural role in establishing the NADH sensitivity of LPD and the PDH complex by restricting movement of the product/substrate NADH, although this amino acid is not directly associated with NAD(H) binding.
    Preview · Article · Feb 2012 · Microbiology
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Bacillus coagulans is a ubiquitous soil bacterium that grows at 50-55 °C and pH 5.0 and ferments various sugars that constitute plant biomass to L (+)-lactic acid. The ability of this sporogenic lactic acid bacterium to grow at 50-55 °C and pH 5.0 makes this organism an attractive microbial biocatalyst for production of optically pure lactic acid at industrial scale not only from glucose derived from cellulose but also from xylose, a major constituent of hemicellulose. This bacterium is also considered as a potential probiotic. Complete genome sequence of a representative strain, B. coagulans strain 36D1, is presented and discussed.
    Full-text · Article · Dec 2011 · Standards in Genomic Sciences
  • [Show abstract] [Hide abstract]
    ABSTRACT: Escherichia coli KO11 (ATCC 55124) was engineered in 1990 to produce ethanol by chromosomal insertion of the Zymomonas mobilis pdc and adhB genes into E. coli W (ATCC 9637). KO11FL, our current laboratory version of KO11, and its parent E. coli W were sequenced, and contigs assembled into genomic sequences using optical NcoI restriction maps as templates. E. coli W contained plasmids pRK1 (102.5 kb) and pRK2 (5.4 kb), but KO11FL only contained pRK2. KO11FL optical maps made with AflII and with BamHI showed a tandem repeat region, consisting of at least 20 copies of a 10-kb unit. The repeat region was located at the insertion site for the pdc, adhB, and chloramphenicol-resistance genes. Sequence coverage of these genes was about 25-fold higher than average, consistent with amplification of the foreign genes that were inserted as circularized DNA. Selection for higher levels of chloramphenicol resistance originally produced strains with higher pdc and adhB expression, and hence improved fermentation performance, by increasing the gene copy number. Sequence data for an earlier version of KO11, ATCC 55124, indicated that multiple copies of pdc adhB were present. Comparison of the W and KO11FL genomes showed large inversions and deletions in KO11FL, mostly enabled by IS10, which is absent from W but present at 30 sites in KO11FL. The early KO11 strain ATCC 55124 had no rearrangements, contained only one IS10, and lacked most accumulated single nucleotide polymorphisms (SNPs) present in KO11FL. Despite rearrangements and SNPs in KO11FL, fermentation performance was equal to that of ATCC 55124.
    No preview · Article · Nov 2011 · Journal of Industrial Microbiology
  • Source
    Qingzhao Wang · Lonnie O Ingram · K T Shanmugam
    [Show abstract] [Hide abstract]
    ABSTRACT: Lactic acid, an attractive, renewable chemical for production of biobased plastics (polylactic acid, PLA), is currently commercially produced from food-based sources of sugar. Pure optical isomers of lactate needed for PLA are typically produced by microbial fermentation of sugars at temperatures below 40 °C. Bacillus coagulans produces L(+)-lactate as a primary fermentation product and grows optimally at 50 °C and pH 5, conditions that are optimal for activity of commercial fungal cellulases. This strain was engineered to produce D(-)-lactate by deleting the native ldh (L-lactate dehydrogenase) and alsS (acetolactate synthase) genes to impede anaerobic growth, followed by growth-based selection to isolate suppressor mutants that restored growth. One of these, strain QZ19, produced about 90 g L(-1) of optically pure D(-)-lactic acid from glucose in < 48 h. The new source of D-lactate dehydrogenase (D-LDH) activity was identified as a mutated form of glycerol dehydrogenase (GlyDH; D121N and F245S) that was produced at high levels as a result of a third mutation (insertion sequence). Although the native GlyDH had no detectable activity with pyruvate, the mutated GlyDH had a D-LDH specific activity of 0.8 μmoles min(-1) (mg protein)(-1). By using QZ19 for simultaneous saccharification and fermentation of cellulose to D-lactate (50 °C and pH 5.0), the cellulase usage could be reduced to 1/3 that required for equivalent fermentations by mesophilic lactic acid bacteria. Together, the native B. coagulans and the QZ19 derivative can be used to produce either L(+) or D(-) optical isomers of lactic acid (respectively) at high titers and yields from nonfood carbohydrates.
    Full-text · Article · Nov 2011 · Proceedings of the National Academy of Sciences
  • [Show abstract] [Hide abstract]
    ABSTRACT: Microaeration (injecting air into the headspace) improved the fermentation of hemicellulose hydrolysates obtained from the phosphoric acid pretreatment of sugarcane bagasse at 170°C for 10 min. In addition, with 10% slurries of phosphoric acid pretreated bagasse (180°C, 10 min), air injection into the headspace promoted xylose utilization and increased ethanol yields from 0.16 to 0.20 g ethanol/g bagasse dry weight using a liquefaction plus simultaneous saccharification and co-fermentation process (L+SScF). This process was scaled up to 80 L using slurries of acid pretreated bagasse (96 h incubation; 0.6L of air/min into the headspace) with ethanol yields of 312-347 L (82-92 gal) per tone (dry matter), corresponding to 0.25 and 0.27 g/g bagasse (dry weight). Injection of small amounts of air into the headspace may provide a convenient alternative to subsurface sparging that avoids problems of foaming, sparger hygiene, flotation of particulates, and phase separation.
    No preview · Article · Jul 2011 · Bioresource Technology
  • Source
    X Wang · E N Miller · L P Yomano · X Zhang · K T Shanmugam · L O Ingram
    [Show abstract] [Hide abstract]
    ABSTRACT: Furfural is an important fermentation inhibitor in hemicellulose sugar syrups derived from woody biomass. The metabolism of furfural by NADPH-dependent oxidoreductases, such as YqhD (low Km for NADPH), is proposed to inhibit the growth and fermentation of xylose in Escherichia coli by competing with biosynthesis for NADPH. The discovery that the NADH-dependent propanediol oxidoreductase (FucO) can reduce furfural provided a new approach to improve furfural tolerance. Strains that produced ethanol or lactate efficiently as primary products from xylose were developed. These strains included chromosomal mutations in yqhD expression that permitted the fermentation of xylose broths containing up to 10 mM furfural. Expression of fucO from plasmids was shown to increase furfural tolerance by 50% and to permit the fermentation of 15 mM furfural. Product yields with 15 mM furfural were equivalent to those of control strains without added furfural (85% to 90% of the theoretical maximum). These two defined genetic traits can be readily transferred to enteric biocatalysts designed to produce other products. A similar strategy that minimizes the depletion of NADPH pools by native detoxification enzymes may be generally useful for other inhibitory compounds in lignocellulosic sugar streams and with other organisms.
    Full-text · Article · Jun 2011 · Applied and Environmental Microbiology
  • Qingzhao Wang · Xueming Zhao · Jauhleene Chamu · K T Shanmugam
    [Show abstract] [Hide abstract]
    ABSTRACT: The high fermentation cost of lactic acid is a barrier for polylactic acid (PLA) to compete with the petrochemical derived plastics. In order to lower the cost of lactic acid, the industry needs a microorganism that can ferment various sugars at high temperature (50°C) and at the same time using low cost mineral salts (MS) medium. One such bacterium, BL1, was isolated at 50°C and identified as Bacillus licheniformis. BL1 can ferment glucose to optically pure l-lactate with a maximum specific productivity of 7.8 g/hl in LB medium and 0.7 g/hl in MS medium at 50°C. BL1 can also consume 10% and 15% glucose in 20 and 48 h, respectively. After serial transfer of BL1 and BL2 in different concentrations of xylose and MS medium respectively, the final mutant BL3 could efficiently ferment glucose and xylose with specific productivity of 1.9 g/hl and 1.2g/hl in strict MS medium.
    No preview · Article · Jun 2011 · Bioresource Technology
  • Mark S Ou · Lonnie O Ingram · K T Shanmugam
    [Show abstract] [Hide abstract]
    ABSTRACT: Lactic acid is used as an additive in foods, pharmaceuticals, and cosmetics, and is also an industrial chemical. Optically pure lactic acid is increasingly used as a renewable bio-based product to replace petroleum-based plastics. However, current production of lactic acid depends on carbohydrate feedstocks that have alternate uses as foods. The use of non-food feedstocks by current commercial biocatalysts is limited by inefficient pathways for pentose utilization. B. coagulans strain 36D1 is a thermotolerant bacterium that can grow and efficiently ferment pentoses using the pentose-phosphate pathway and all other sugar constituents of lignocellulosic biomass at 50°C and pH 5.0, conditions that also favor simultaneous enzymatic saccharification and fermentation (SSF) of cellulose. Using this bacterial biocatalyst, high levels (150-180 g l(-1)) of lactic acid were produced from xylose and glucose with minimal by-products in mineral salts medium. In a fed-batch SSF of crystalline cellulose with fungal enzymes and B. coagulans, lactic acid titer was 80 g l(-1) and the yield was close to 80%. These results demonstrate that B. coagulans can effectively ferment non-food carbohydrates from lignocellulose to L: (+)-lactic acid at sufficient concentrations for commercial application. The high temperature fermentation of pentoses and hexoses to lactic acid by B. coagulans has these additional advantages: reduction in cellulase loading in SSF of cellulose with a decrease in enzyme cost in the process and a reduction in contamination of large-scale fermentations.
    No preview · Article · May 2011 · Journal of Industrial Microbiology
  • [Show abstract] [Hide abstract]
    ABSTRACT: Previous results have demonstrated that the silencing of adjacent genes encoding NADPH-dependent furfural oxidoreductases (yqhD dkgA) is responsible for increased furfural tolerance in an E. coli strain EMFR9 [Miller et al., Appl Environ Microbiol 75:4315-4323, 2009]. This gene silencing is now reported to result from the spontaneous insertion of an IS10 into the coding region of yqhC, an upstream gene. YqhC shares homology with transcriptional regulators belonging to the AraC/XylS family and was shown to act as a positive regulator of the adjacent operon encoding YqhD and DkgA. Regulation was demonstrated by constructing a chromosomal deletion of yqhC, a firefly luciferase reporter plasmid for yqhC, and by a direct comparison of furfural resistance and NADPH-dependent furfural reductase activity. Closely related bacteria contain yqhC, yqhD, and dkgA orthologs in the same arrangement as in E. coli LY180. Orthologs of yqhC are also present in more distantly related Gram-negative bacteria. Disruption of yqhC offers a useful approach to increase furfural tolerance in bacteria.
    No preview · Article · Mar 2011 · Journal of Industrial Microbiology

Publication Stats

6k Citations
476.33 Total Impact Points


  • 1983-2015
    • University of Florida
      • Department of Microbiology and Cell Science
      Gainesville, Florida, United States
  • 1995
    • University of California, Los Angeles
      • Department of Microbiology, Immunology, and Molecular Genetics
      Los Angeles, California, United States
  • 1991-1994
    • University of Georgia
      • Department of Microbiology
      Атина, Georgia, United States
  • 1976-1983
    • University of California, Davis
      • Department of Plant Sciences
      Davis, California, United States
  • 1969
    • Honolulu University
      Honolulu, Hawaii, United States