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1.
Céline Boileau Richard Auria Sylvain Davidson Laurence Casalot Pierre Christen Pierre-Pol Liebgott Yannick Combet-Blanc 《Biotechnology for biofuels》2016,9(1):269
Background
Thermotoga maritima and T. neapolitana are hyperthermophile bacteria chosen by many research teams to produce bio-hydrogen because of their potential to ferment a wide variety of sugars with the highest theoretical H2/glucose yields. However, to develop economically sustainable bio-processes, the culture medium formulation remained to be optimized. The main aim of this study was to quantify accurately and specifically the effect of thiosulfate, used as sulfured nutriment model, on T. maritima growth, yields and productivities of hydrogen. The results were obtained from batch cultures, performed into a bioreactor, carefully controlled, and specifically designed to prevent the back-inhibition by hydrogen.Results
Among sulfured nutriments tested, thiosulfate, cysteine, and sulfide were found to be the most efficient to stimulate T. maritima growth and hydrogen production. In particular, under our experimental conditions (glucose 60 mmol L?1 and yeast extract 1 g L?1), the cellular growth was limited by thiosulfate concentrations lower than 0.06 mmol L?1. Under these conditions, the cellular yield on thiosulfate (Y X/Thio) could be determined at 3617 mg mmol?1. In addition, it has been shown that the limitations of T. maritima growth by thiosulfate lead to metabolic stress marked by a significant metabolic shift of glucose towards the production of extracellular polysaccharides (EPS). Finally, it has been estimated that the presence of thiosulfate in the T. maritima culture medium significantly increased the cellular and hydrogen productivities by a factor 6 without detectable sulfide production.Conclusions
The stimulant effects of thiosulfate at very low concentrations on T. maritima growth have forced us to reconsider its role in this species and more probably also in all thiosulfato-reducer hyperthermophiles. Henceforth, thiosulfate should be considered in T. maritima as (1) an essential sulfur source for cellular materials when it is present at low concentrations (about 0.3 mmol g?1 of cells), and (2) as both sulfur source and detoxifying agent for H2 when thiosulfate is present at higher concentrations and, when, simultaneously, the pH2 is high. Finally, to improve the hydrogen production in bio-processes using Thermotoga species, it should be recommended to incorporate thiosulfate in the culture medium.2.
Objectives
To improve H2 production, the green algae Chlamydomonas reinhardtii cc849 was co-cultured with Azotobacter chroococcum.Results
The maximum H2 production of the co-culture was 350% greater than that of the pure algal cultures under optimal H2 production conditions. The maximum growth and the respiratory rate of the co-cultures were about 320 and 300% of the controls, and the dissolved O2 of co-cultures was decreased 74%. Furthermore, the in vitro maximum hydrogenase activity of the co-culture was 250% greater than that of the control, and the in vivo maximum hydrogenase activity of the co-culture was 1.4-fold greater than that of the control. In addition, the maximum starch content of co-culture was 1400% that of the control.Conclusions
Azotobacter chroococcum improved the H2 production of the co-cultures by decreasing the O2 content and increasing the growth and starch content of the algae and the hydrogenase activity of the co-cultures relative to those of pure algal cultures.3.
Objective
Palladised cells of Desulfovibrio desulfuricans and Shewanella oneidensis have been reported as fuel cell electrocatalysts but growth at scale may be unattractive/costly; we have evaluated the potential of using E. coli, using H2/formate for Pd-nanoparticle manufacture.Results
Using ‘bio-Pd’ made under H2 (20 wt%) cyclic voltammograms suggested electrochemical activity of bio-NPs in a native state, attributed to proton adsorption/desorption. Bio-Pd prepared using formate as the electron donor gave smaller, well separated NPs; this material showed no electrochemical properties, and hence little potential for fuel cell use using a simple preparation technique. Bio-Pd on S. oneidensis gave similar results to those obtained using E. coli.Conclusion
Bio-Pd is sufficiently conductive to make an E. coli-derived electrochemically active material on intact, unprocessed bacterial cells if prepared at the expense of H2, showing potential for fuel cell applications using a simple one-step preparation method.4.
5.
Han Bin Pek Pei Yu Lim Chengcheng Liu Dong-Yup Lee Xuezhi Bi Fong Tian Wong Dave Siak-Wei Ow 《Biotechnology letters》2017,39(5):759-765
Objectives
To evaluate the secretory and cytoplasmic expression of a thermostable Thermogata maritima invertase in Lactococcus lactis.Results
The thermostable invertase from T. maritima was cloned with and without the USP45 secretory peptide into the pNZ8148 vector for nisin-inducible expression in L. lactis. The introduction of an USP45 secretion peptide at the N-terminal of the enzyme led to a loss of protein solubility. Computational homology modeling and hydrophobicity studies indicated that the USP45 peptide exposes a stretch of hydrophobic amino acids on the protein surface resulting in lower solubility. Removal of the USP45 secretion peptide allowed a soluble and functional invertase to be expressed intracellularly in L. lactis. Immobilized metal affinity chromatography purification of the cell lysate with nickel-NTA gave a single protein band on SDS-PAGE, while E. coli-expressed invertase consistently co-purified with an additional band. The yields of the purified invertase from E. coli and L. lactis were 14.1 and 6.3 mg/l respectively.Conclusions
Invertase can be expressed in L. lactis and purified in a functional form. L. lactis is a suitable host for the production of food-grade invertase for use in the food and biotechnology industries.6.
Background
Caldicellulosiruptor saccharolyticus has the ability to produce hydrogen (H2) at high yields from a wide spectrum of carbon sources, and has therefore gained industrial interest. For a cost-effective biohydrogen process, the ability of an organism to tolerate high partial pressures of H2 (PH2) is a critical aspect to eliminate the need for continuous stripping of the produced H2 from the bioreactor.Results
Herein, we demonstrate that, under given conditions, growth and H2 production in C. saccharolyticus can be sustained at PH2 up to 67 kPa in a chemostat. At this PH2, 38% and 16% of the pyruvate flux was redirected to lactate and ethanol, respectively, to maintain a relatively low cytosolic NADH/NAD ratio (0.12 mol/mol). To investigate the effect of the redox ratio on the glycolytic flux, a kinetic model describing the activity of the key glycolytic enzyme, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), was developed. Indeed, at NADH/NAD ratios of 0.12 mol/mol (K i of NADH = 0.03 ± 0.01 mM) GAPDH activity was inhibited by only 50% allowing still a high glycolytic flux (3.2 ± 0.4 mM/h). Even at high NADH/NAD ratios up to 1 mol/mol the enzyme was not completely inhibited. During batch cultivations, hydrogen tolerance of C. saccharolyticus was dependent on the growth phase of the organism as well as the carbon and energy source used. The obtained results were analyzed, based on thermodynamic and enzyme kinetic considerations, to gain insight in the mechanism underlying the unique ability of C. saccharolyticus to grow and produce H2 under relatively high PH2.Conclusion
C. saccharolyticus is able to grow and produce hydrogen at high PH2, hence eliminating the need of gas sparging in its cultures. Under this condition, it has a unique ability to fine tune its metabolism by maintaining the glycolytic flux through regulating GAPDH activity and redistribution of pyruvate flux. Concerning the later, xylose-rich feedstock should be preferred over the sucrose-rich one for better H2 yield.7.
Objectives
To enhance succinic acid production in Corynebacterium glutamicum by increasing the supply of NADH and the rate of glucose consumption by decreasing H+-ATPase activity.Results
A mutant of C. glutamicum NC-3-1 with decreased H+-ATPase activity was constructed. This increased the rate of glycolysis and the supply of NADH. Fermentation of C. glutamicum NC-3-1 gave 39 % higher succinic acid production (113 and 81 g/l), a 29 % higher succinic acid yield (0.94 and 0.73 g succinic acid/g glucose) and decreased by-products formation compared to that of C. glutamicum NC-3 in 5 l bioreactor.Conclusion
The point mutation in C. glutamicum NC-3-1 increased the rate of glycolysis and resulted in higher succinic acid production, higher succinic acid yield and significantly decreased formation of by-products.8.
Young-Saeng Kim Il-Sup Kim Joseph S. Boyd Arnaud Taton James W. Golden Ho-Sung Yoon 《Biotechnology letters》2017,39(10):1499-1507
Objectives
To improve the oxidative stress tolerance, biomass yield, and ascorbate/dehydroascorbate (AsA/DHA) ratio of Synechococcus elongatus PCC 7942 in the presence of H2O2, by heterologous expression of the dehydroascorbate reductase (DHAR) gene from Brassica juncea (BrDHAR).Results
Under H2O2 stress, overexpression of BrDHAR in the transgenic strain (BrD) of S. elongatus greatly increased the AsA/DHA ratio. As part of the AsA recycling system, the oxidative stress response induced by reactive oxygen species was enhanced, and intracellular H2O2 level decreased. In addition, under H2O2 stress conditions, the BrD strain displayed increased growth rate and biomass, as well as higher chlorophyll content and deeper pigmentation than did wild-type and control strains.Conclusion
By maintaining the AsA pool and redox homeostasis, the heterologous expression of BrDHAR increased S. elongatus tolerance to H2O2 stress, improving the biomass yield under these conditions. The results suggest that the BrD strain of S. elongatus, with its ability to attenuate the deleterious effects of ROS caused by environmental stressors, could be a promising platform for the generation of biofuels and other valuable bioproducts.9.
Objective
To explore the glycerol utilization pathway in Corynebacterium glutamicum for succinate production under O2 deprivation.Result
Overexpression of a glycerol facilitator, glycerol dehydrogenase and dihydroxyacetone kinase from Escherichia coli K-12 in C. glutamicum led to recombinant strains NC-3G diverting glycerol utilization towards succinate production under O2 deprivation. Under these conditions, strain NC-3G efficiently consumed glycerol and produced succinate without growth. The recombinant C. glutamicum utilizing glycerol as the sole carbon source showed higher intracellular NADH/NAD+ ratio compare with utilizing glucose. The mass conversion of succinate increased from 0.64 to 0.95. Using an anaerobic fed-batch fermentation process, the final strain produced 38.4 g succinate/l with an average yield of 1.02 g/g.Conclusions
The metabolically-engineered strains showed an efficient succinate production using glycerol as sole carbon source under O2 deprivation.10.
11.
Objectives
To develop a versatile Trichoderma reesei (teleomorph Hypocrea jecorina) expression system for the high-purity production of heterologous proteins.Results
The versatile T. reesei expression system is based on xyn1 and xyn2 promoters, A824V transition in XYRI, and a bicomponent carbon source strategy. Red fluorescent protein gene rfp and alkaline endoglucanase EGV gene egv3 from Humicola insolens were used as reporter genes to test our versatile expression systemConclusions
The versatile T. reesei expression system can be applied to produce heterologous proteins with high purity and high yield.12.
Objectives
To investigate the feasibility of coupling carbonyl cyanide m-chlorophenylhydrazone-regulated photohydrogen production by Tetraselmis subcordiformis in a photobioreactor to an alkaline fuel cell (AFC).Results
H2 evolution kinetics in the AFC integrated process was characterized. The duration of H2 evolution was prolonged and its yield was improved about 1.5-fold (to 78 ± 5 ml l?1) compared with that of the process without AFC. Improved H2 yield was possibly caused by removal of H2 feedback inhibition by H2 consumption in situ. Decreases in the H2 production rate correlated with the gradual deactivation of PSII and hydrogenase activities. The H2 yield was closely associated with catabolism of starch and protein.Conclusion
A marine green algal CO2-supplemented culture integrated with in situ H2-consumption by an AFC system was developed as a viable protocol for the H2 production.13.
Tatyana Laurinavichene Kestutis Laurinavichius Evgeny Shastik Anatoly Tsygankov 《Biotechnology letters》2018,40(2):309-314
Objectives
To prove the possibility of efficient starch photofermentation in co-culture of heterotrophic and phototrophic bacteria over prolonged period.Results
Repeated batch photofermentation of starch was demonstrated in co-culture Clostridium butyricum and Rhodobacter sphaeroides under microaerobic conditions. It continued 15 months without addition of new inoculum or pH regulation when using 4–5 g starch l?1 and 0.04 g yeast extract l?1. The complete degradation of starch without volatile fatty acids accumulation was shown in this co-culture. The average H2 yield of 5.2 mol/mol glucose was much higher than that in Clostridium monoculture. The species composition of co-culture was studied by q-PCR assay. The concentration of Clostridium cells in prolonged co-culture was lower than in monoculture and even in a single batch co-culture. This means that Clostridia growth was significantly limited whereas starch hydrolysis still took place.Conclusion
The prolonged repeated batch photofermentation of starch by co-culture C. butyricum and R. sphaeroides provided efficient H2 production without accumulation of organic acids under conditions of Clostridia limitation.14.
Background and aims
Low nitrogen negatively affects soil fertility and plant productivity. Glucose-6-phosphate dehydrogenase (G6PDH) and Epichloë gansuensis endophytes are two factors that are associated with tolerance of Achnatherum inebrians to abiotic stress. However, the possibility that E. gansuensis interacts with G6PDH in enhancing low nitrogen tolerance of host grasses has not been examined.Methods
A. inebrians plants with (E+) and without E. gansuensis (E?) were subjected to different nitrogen concentration treatments (0.1, 1, and 7.5 mM). After 90 days, physiological studies were carried out to investigate the participation of G6PDH in the adaption of host plants to low nitrogen availability.Results
Low nitrogen retarded the growth of A. inebrians. E+ plants had higher total dry weight, chlorophyll a and b contents, net photosynthesis rate, G6PDH activity, and GSH content, while having lower plasma membrane (PM) NADPH oxidase activity, NADPH/NADP+ ratios, and MDA and H2O2 than in E? A. inebrians plants under low nitrogen concentration.Conclusions
The presence of E. gansuensis played a key role in maintaining the growth of the A. inebrians plants under low nitrogen concentration by regulating G6PDH activity and the NADPH/NADP+ ratio and improving net photosynthesis rate.15.
Objectives
To enhance acid tolerance of Candida glabrata for pyruvate production by engineering AMP metabolism.Results
The physiological function of AMP deaminase in AMP metabolism from C. glabrata was investigated by deleting or overexpresseing the corresponding gene, CgAMD1. At pH 4, CgAMD1 overexpression resulted in 59 and 51% increases in biomass and cell viability compared to those of wild type strain, respectively. In addition, the intracellular ATP level of strain Cgamd1Δ/CgAMD1 was down-regulated by 22%, which led to a 94% increase in pyruvate production. Further, various strengths of CgAMD1 expression cassettes were designed, thus resulting in a 59% increase in pyruvate production at pH 4. Strain Cgamd1Δ/CgAMD1 (H) was grown in a 30 l batch bioreactor at pH 4, and pyruvate reached 46.1 g/l.Conclusion
CgAMD1 overexpression plays an active role in improving acid tolerance and pyruvate fermentation performance of C. glabrata at pH 4.16.
Chenchen Zhang Jingyu Lu Duo Yang Xia Chen Yujun Huang Ruixia Gu 《Biotechnology letters》2018,40(4):729-735
Objective
To investigate the aerotolerance of Lactobacillus rhamnosus hsryfm 1301 and its influencing factors.Results
The growth rate of L. rhamnosus hsryfm 1301 weakened noticeably when the concentration of supplemented H2O2 reached 1 mM, and only 2% of all L. rhamnosus hsryfm 1301 cells survived in MRS broth supplemented with 2 mM H2O2 for 1 h. After pretreatment with 0.5 mM H2O2, the surviving cells of L. rhamnosus hsryfm 1301 in the presence of 5 mM H2O2 for 1 h increased from 3.7 to 7.8 log CFU. Acid stress, osmotic stress, and heat stress at 46 °C also enhanced its aerotolerance, while heat stress at 50 °C reduced the tolerance of L. rhamnosus hsryfm 1301 to oxidative stress. Moreover, treatment with 0.5 mM H2O2 increased the heat stress tolerance of L. rhamnosus hsryfm 1301 by approximately 150-fold.Conclusions
Lactobacillus rhamnosus hsryfm 1301 possesses a stress-inducible defense system against oxidative stress, and the cross-adaptation to different stresses is a promising target to increase the stress tolerance of L. rhamnosus hsryfm 1301 during probiotic food and starter culture production.17.
Godwin E. Oyiwona James Ogbonna Chukwudi Uzoma Anyanwu So Ishizaki Zen-ichiro Kimura Satoshi Okabe 《Biotechnology letters》2017,39(2):253-259
Objective
To investigate a syntrophic interaction between Geobacter sulfurreducens and hydrogenotrophic methanogens in sludge-inoculated microbial fuel cell (MFC) systems running on glucose with an improved electron recovery at the anode.Results
The presence of archaea in MFC reduces Coulombic efficiency (CE) due to their electron scavenging capability but, here, we demonstrate that a syntrophic interaction can occur between G. sulfurreducens and hydrogenotrophic methanogens via interspecies H2 transfer with improvement in CE and power density. The addition of the methanogenesis inhibitor, 2-bromoethanesulfonate (BES), resulted in the reduction in power density from 5.29 to 2 W/m3, and then gradually increased to the peak value of 5.5 W/m3 when BES addition was stopped.Conclusion
Reduction of H2 partial pressure by archaea is an efficient approach in improving power output in a glucose-fed MFC system using Geobacter sp. as an inoculum.18.
Objectives
To construct a Bacillus subtilis strain for improved uridine production.Results
The AAG2846–2848 fragment of the pyrAB gene, encoding carbamoylphosphate synthetase, was deleted in B. subtilis TD246 leading to a 245% increase of uridine production and the conversion from glucose to uridine increased by 10.5%. Overexpression of the pyr operon increased the production of uridine by a further 31% and the conversion rate of glucose to uridine was increased by 18%. In addition, the blocking of arginine synthesis or disabling of glutamate dehydrogenase significantly enhanced the uridine production. The highest-producing strain, B. subtilis TD297, accumulated 11 g uridine/l with a yield of 240 mg uridine/g glucose in shake-flask cultivation.Conclusion
This is the first report of engineered B. subtilis strains which can produce more than 11 g uridine/l, with a yield reaching 240 mg uridine/g glucose in shake-flask cultivation.19.
Korey J. Brownstein Mahmoud Gargouri William R. Folk David R. Gang 《Metabolomics : Official journal of the Metabolomic Society》2017,13(11):133
Introduction
Botanicals containing iridoid and phenylethanoid/phenylpropanoid glycosides are used worldwide for the treatment of inflammatory musculoskeletal conditions that are primary causes of human years lived with disability, such as arthritis and lower back pain.Objectives
We report the analysis of candidate anti-inflammatory metabolites of several endemic Scrophularia species and Verbascum thapsus used medicinally by peoples of North America.Methods
Leaves, stems, and roots were analyzed by ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) and partial least squares-discriminant analysis (PLS-DA) was performed in MetaboAnalyst 3.0 after processing the datasets in Progenesis QI.Results
Comparison of the datasets revealed significant and differential accumulation of iridoid and phenylethanoid/phenylpropanoid glycosides in the tissues of the endemic Scrophularia species and Verbascum thapsus.Conclusions
Our investigation identified several species of pharmacological interest as good sources for harpagoside and other important anti-inflammatory metabolites.20.