Initial Glucose Concentration Research Articles

Simultaneous delignification and saccharification of rice straw as a lignocellulosic biomass by immobilized Thrichoderma viride sp. to enhance enzymatic sugar production

Simultaneous biological delignification and saccharification of rice straw by the immobilized Trichoderma viride cells were studied in this work. Response surface methodology as a multiple responses optimization technique was utilized to optimize several important factors such as the biomass content of the medium (w/v), inoculum size and agitation rate. Results indicated that at the obtained optimum conditions the lignin removal efficiency of 74% and sugar concentration equal to 8.52 g/L could be achieved in ten days of pretreatment. In addition, the influence of initial glucose concentration in the medium on both the pretreatment saccharification and the subsequent enzymatic hydrolysis efficiencies was investigated. It was revealed that the higher initial glucose concentration is beneficial to obtain higher total saccharification efficiency from pretreatment and the following enzymatic hydrolysis and a total efficiency equal to 81% was obtained for 15 g/L initial glucose concentration. Accordingly, it can be concluded that the immobilized Trichoderma viride in this work can be considered as a potentially applicable strain to design a promising lignocellulosic materials bio-pretreatment process.

Effectively enhancing acetone concentration and acetone/butanol ratio in ABE fermentation by a glucose/acetate co-substrate system incorporating with glucose limitation and C. acetobutylicum/S. cerevisiae co-culturing

A novel glucose/acetate co-substrate system incorporating with C. acetobutylicum/S. cerevisiae co-culturing and glucose limitation was proposed and applied in ABE fermentations by C. acetobutylicum. With this strategy, acetone production was enhanced while NADH dependent butanol synthesis rate was adequately restricted by glucose limitation via decreasing initial glucose concentration in the medium and adaptively adding acetate/S. cerevisiae during solventogenic phase. Under these conditions, acetone production ability of C. acetobutylicum could be fully utilized by delaying butanol inhibition occurrence time; favorable environment for acetone production was created while incomplete ABE fermentation due to glucose limitation avoided. The proposed strategy could arbitrarily control or maximize acetone concentration and acetone/butanol ratio (A/B) in the ranges of 6–12g/L and 0.5–1.0, the maximum values could reach the levels of 11.74g/L and 1.02 which would potentially promote ABE fermentative products flexibility and bio-acetone productions using renewable biomass. The theoretical analysis of A/B ratio based on carbon mass and energy balances showed that, the maximum A/B ratio of 1.04 could be achieved when 60g/L glucose and 12g/L acetate were consumed by C. acetobutylicum, which coincided with the experimental data (1.02) well.

Characteristics of hydrogen and bioflocculant production by a transposon-mutagenized strain of Pantoea agglomerans BH18

Based on the transposon-mutagenized library of Pantoea agglomerans BH18, the mutant strain 2-103 was obtained using mutant screens for high simultaneous production of hydrogen and bioflocculant. The mutant strain 2-103 was able to grow in medium with 50 μg/mL of kanamycin and could be amplified using Tn7-based transposon PCR amplification in cells from several passages, indicating that the mutant strain 2-103 transposon insertion was stable. The mutant strain 2-103 cell culture from batch experiments with varying initial pH values, glucose concentrations and NaCl concentrations was determined. The result indicated that the optimum initial pH for hydrogen production and bioflocculant activity was 7.0 and 8.0, respectively. The optimal glucose concentration for hydrogen and bioflocculant production was 20 g/L. In addition, the mutant strain 2-103 could produce hydrogen and bioflocculant under marine and fresh culture conditions. The mutant strain 2-103 had the highest production of hydrogen and bioflocculant with (1.55 ± 0.07) mol H2/mol glucose and (83.7 ± 5.89)% under marine culture conditions, which increased to (1.78 ± 0.08) mol H2/mol glucose and (93.5 ± 6.24)% under fresh culture conditions. This study found that the mutant strain 2-103 has the ability to produce hydrogen and bioflocculant within a range of initial pH values, glucose and NaCl concentrations, which is beneficial for the improvement of cost-effective bio-treatment processes.

Reversal of Diabetes in NOD Mice by Clinical-Grade Proinsulin and IL-10-Secreting Lactococcus lactis in Combination With Low-Dose Anti-CD3 Depends on the Induction of Foxp3-Positive T Cells.

The introduction of β-cell autoantigens via the gut through Lactococcus lactis (L. lactis) has been demonstrated to be a promising approach for diabetes reversal in NOD mice. Here we show that a combination therapy of low-dose anti-CD3 with a clinical-grade self-containing L. lactis, appropriate for human application, secreting human proinsulin and interleukin-10, cured 66% of mice with new-onset diabetes, which is comparable to therapy results with plasmid-driven L. lactis Initial blood glucose concentrations (<350 mg/dL) and insulin autoantibody positivity were predictors of the stable reversal of hyperglycemia, and decline in insulin autoantibody positivity was an immune biomarker of therapeutic outcome. The assessment of the immune changes induced by the L. lactis-based therapy revealed elevated frequencies of CD4+Foxp3+ T cells in the pancreas-draining lymph nodes, pancreas, and peripheral blood of all treated mice, independent of metabolic outcome. Neutralization of cytotoxic T-lymphocyte antigen 4 and transforming growth factor-β partially abrogated the suppressive function of therapy-induced regulatory T cells (Tregs). Ablation or functional impairment of Foxp3+ Tregs in vivo at the start or stop of therapy impaired immune tolerance, highlighting the dependence of the therapy-induced tolerance in mice with new-onset diabetes on the presence and functionality of CD4+Foxp3+ T cells. Biomarkers identified in this study can potentially be used in the future to tailor the L. lactis-based combination therapy for individual patients.

The Effect of Early Feeding on Initial Glucose Concentrations in Term Newborns

To evaluate the influence of early feeding on initial glucose concentrations in healthy term newborns who were not at risk for hypoglycemia. This retrospective observational study was conducted at the University of Arkansas for Medical Sciences where universal early glucose screening was standard of care for newborn infants. Plasma glucose concentrations were compared in term infants born in 2008 who were not at risk for neonatal hypoglycemia and who were fed before (early feeders) and after (late feeders) their initial glucose screens. Multiple linear regression models were built to determine whether glucose concentrations differed significantly between early vs late feeders. In the 315 early and 572 late feeders, the mean (SD) age of first feeding was 0.9 (0.6) and 3.8 (2.0) hours, respectively. The age at initial glucose specimen collection was 2.2 (1.1) and 1.8 (0.8) hours, respectively. The initial glucose concentration was not higher in early vs late feeders (51.8 ± 11.9 vs 55.5 ± 13.3 mg/dL; P < .001). In linear regression analyses of all infants, the mean initial glucose concentration was 3.61 (95% CI 1.75-5.48) mg/dL lower in early vs late feeders. Early feeding in otherwise healthy term newborns did not increase initial glucose concentrations compared with newborns who fed later (ie, fasted). Before direct evidence is available, these observations may be instructive for managing early asymptomatic hypoglycemia in at-risk newborns.

Microbial Succession in Spontaneously Fermented Grape Must Before, During and After Stuck Fermentation

The microbial succession in spontaneously fermenting Riesling must was investigated from the beginning (pressing) until the end (sulphuring) of the fermentation in two harvest years (2008 and 2009) at a Moselle winery (Germany). In both years, the fermentation was interrupted by a stuck period. The length of the stuck period varied considerably (20 weeks in 2008 and one week in 2009). Different yeasts (Candida, Debaryomyces, Pichia, Hanseniaspora, Saccharomyces, Metschnikowia, Cryptococcus, Filobasidium and Rhodotorula) and bacteria (Gluconobacter, Asaia, Acetobacter, Oenococcus, Lactobacillus, Bacillus and Paenibacillus) were isolated successively by plating. The main fermenting organism was Saccharomyces uvarum. Specific primers were developed for S. uvarum, H. uvarum and C. boidinii, followed by the determination of the total cell counts with qPCR. The initial glucose concentration differed between the two years and was 116 g/L in 2008 and 85.4 g/L in 2009. Also, the fructose concentrations were different in both years (114 g/L in 2008 and 77.8 g/L in 2009). The stuck period appeared when the glucose/fructose ratio was 0.34 and 0.12 respectively. The microbiota changed during the stuck period.

Hypoglycaemia in hospitalised neonatal calves: Prevalence, associated conditions and impact on prognosis

Hypoglycaemia has traditionally been associated with neonatal diarrhoea and endotoxaemia in calves, but the clinical relevance of this finding in spontaneously diseased calves has not previously been evaluated. To determine the prevalence and prognostic relevance of severe hypoglycaemia (plasma glucose concentration < 2 mmol/L), data from 10,060 hospitalised calves (≤21 days of age) were retrospectively analysed. Additionally, clinical findings and diagnoses in a subset of 100 calves with severe hypoglycaemia were compared with those in 100 randomly selected calves with initial plasma glucose concentrations in the reference range (4.4–6.9 mmol/L).The prevalence of severe hypoglycaemia in the whole study sample was 6.3%. Severe hypoglycaemia was associated with a poor survival rate of 20.6% vs. 74.0% discharged animals in the group of calves with initial normoglycaemia. Review of medical records revealed that severe hypoglycaemia was significantly associated with clinical or necropsy evidence of septicaemia, hypothermia, history or clinical evidence of malnutrition, and peritonitis of varied origin, but not with the presence of neonatal diarrhoea. Only 10 of 100 calves with severe hypoglycaemia showed central nervous involvement such as seizures and opisthotonus. In conclusion, severe hypoglycaemia has a low prevalence in diseased calves in a hospital setting, but is associated with serious health problems and therefore a high risk of non-survival. Severe hypoglycaemia was not easily diagnosed based on clinical signs, but should be suspected in calves with clinical evidence of septicaemia, hypothermia, acute abdominal emergencies, and a history or clinical evidence of malnutrition.

Screening of novel bacteria for the 2,3-butanediol production.

Biotechnologically produced 2,3-butanediol (2,3-BDO) is a potential starting material for industrial bulk chemicals such as butadiene or methyl ethyl ketone which are currently produced from fossil feedstocks. So far, the highest 2,3-BDO concentrations have been obtained with risk group 2 microorganisms. In this study, three risk group 1 microorganisms are presented that are so far unknown for an efficient production of 2,3-BDO. The strains Bacillus atrophaeus NRS-213, Bacillus mojavensis B-14698, and Bacillus vallismortis B-14891 were evaluated regarding their ability to produce high 2,3-BDO concentrations with a broad range of different carbon sources. A maximum 2,3-BDO concentration of 60.4g/L was reached with the strain B. vallismortis B-14891 with an initial glucose concentration of 200g/L within 55h in a batch cultivation. Besides glucose, B. vallismortis B-14891 converts 14 different substrates that can be obtained from residual biomass sources to 2,3-BDO. Therefore B. vallismortis B-14891 is a promising candidate for the large-scale production of 2,3-BDO with low-cost substrates.

Enhanced effectiveness of Rhizopus oryzae by immobilization in a static bed fermentor for l -lactic acid production

Abstract The static bed fermentor was successfully employed for cell immobilization in this study. By complete immobilization of Rhizopus oryzae on a fibrous matrix, cell-free fermentation broth resulted in improved mass transfer and easy operation compared with free cell fermentation in a typical stirred fermentor. Environmental conditions generated in this fermentor configuration favoring the immobilized R. oryzae to grow and produce lactic acid without substrate repression at high initial glucose concentration during batch cultivation. Approximately 67% of the theoretical lactate yield (0.50 g/g) with the productivity of 1.05 g/L h and the final titer of 75.28 g/L was obtained from fermentation with high glucose concentration (150 g/L). Complete cell immobilization supported the continuous operation of lactic acid production by R. oryzae since cell wash out was diminished. When operating the continuous culture at an appropriate dilution rate, a sufficiently high concentration of lactic acid (72.32 g/L) with a small amount of remaining glucose (

Case 2: Neonate with Cholestasis, Thrombocytopenia, and Hypoglycemia

A male infant is born at 36 4/7 weeks’ gestation to a 23-year-old gravida 1, para 0 woman via spontaneous vaginal delivery. He is admitted to the intensive care nursery for growth restriction, hypoglycemia, and thrombocytopenia. The prenatal history is unremarkable. Routine resuscitation is performed in the delivery room. Apgar scores are 8 and 9 at 1 and 5 minutes, respectively. The admission weight is 1.67 kg (0.3 percentile), length 43.0 cm (3.1 percentile), and head circumference 30.0 cm (4.4 percentile). Vital signs at admission and physical examination findings are within normal limits. Admission laboratory values are remarkable for a platelet count of 25 × 103/μL (25 × 109/L), with the remainder of the complete blood cell count within normal limits. Initial glucose concentration by dextrose stick is 20 mg/dL (1.11 mmol/L). By day 2, the infant requires 20% dextrose for persistent hypoglycemia and 2 platelet transfusions. Laboratory tests reveal a total bilirubin of 11.4 mg/dL (195 μmol/L), direct bilirubin of 6.3 mg/dL (108 μmol/L), and aspartate aminotransferase of 107 U/L (1.8 μkat/L). C-reactive protein is elevated, at 4.5 mg/L (42.8 nmol/L). Significant coagulopathy is noted, with an international normalized ratio of 10 on day 3, and the infant receives additional doses of vitamin K, cryoprecipitate, and fresh frozen plasma. Given this early presentation of liver disease, intravenous immunoglobulin is administered, with a consideration of gestational alloimmune liver …

Effects of yeast combined with chromium propionate on growth performance and carcass quality of finishing steers.

A combination of yeast and chromium propionate (Y+Cr) was added to the diets of crossbred finishing steers ( = 504; 402 kg ± 5.76 initial BW) to evaluate impact on feedlot performance and carcass traits. We hypothesized supplementation of Y+Cr would increase growth of feedlot steers. Steers with initial plasma glucose concentrations ≤6.0 m were stratified by initial BW and randomly allocated, within strata, to receive 0 (control) or 3.3 g/d Y+Cr. Steers were further divided into heavy and light weight blocks with 6 pens/diet within each weight block. Cattle were housed in dirt-surfaced pens with 21 steers/pen and had ad libitum access to feed. Body weights were measured at 21-d intervals. Blood samples were collected on d 49 and 94 from a subset of steers (5/pen) for analyses of plasma glucose and lactate concentrations. At the end of the finishing phase, animals were weighed and transported 450 km to an abattoir in Holcomb, KS. Severity of liver abscesses and HCW were collected the day of harvest, and after 36 h of refrigeration, USDA yield and quality grades, LM area, and 12th rib subcutaneous fat thickness were determined. There were no treatment × time × weight block interactions ( > 0.05) and no treatment × block interaction for ADG, DMI, or final BW ( ≥ 0.06), but a treatment × block interaction ( = 0.03) was observed for G:F, in which control, light cattle had poorer efficiency compared with other groups. Treatment × weight group interactions were observed for overall yield grade and carcasses that graded yield grade 1 ( ≤ 0.04). Light steers supplemented with Y+Cr had decreased overall yield grade and increased percentage of carcasses grading yield grade 1 compared with their control counterparts, with no differences observed for heavy steers. Regardless of weight group, a greater percentage of carcasses from steers supplemented with Y+Cr graded yield grade 2 ( = 0.03) and fewer carcasses from steers supplemented Y+Cr graded yield grade 3 ( < 0.01) than control steers. No interactions or effects of treatment were detected for other carcass measurements ( ≥ 0.07). There were no treatment × weight group interactions or effects of treatment for plasma glucose or lactate concentrations on d 49 or 94 ( > 0.10). Overall, yeast in combination with chromium propionate may improve feed efficiency and decrease yield grade of light cattle but had no effect on remaining carcass traits and blood constituents.

Fermentation of mixed substrates by Clostridium pasteurianum and its physiological, metabolic and proteomic characterizations.

BackgroundClostridium pasteurianum is becoming increasingly attractive for the production of chemicals and fuels such as n-butanol and 1,3-propanediol. Previously we have shown that dual substrate fermentation using glucose and glycerol enhanced the cell growth and butanol production significantly. Although C. pasteurianum can grow efficiently with either glucose or glycerol alone, under certain conditions, glucose limitation in the mixed substrate fermentation leads to growth cessation. To understand this phenomenon and for process optimization, fermentation experiments were performed in the presence of excess glycerol but with varied initial concentrations of glucose which were followed by physiological, metabolic and proteomic analyses.ResultsPhysiological characterization showed that the observed cease of growth is not due to the toxicity of n-butanol. Furthermore, the growth can be resumed by addition of glucose or the intermediate oxaloacetate. Proteomic analysis shed more light on the system-level regulation of many proteins directly or indirectly associated with this phenomenon. Surprisingly, it is found that the specific growth rate of C. pasteurianum in the different growth phases (e.g. before and after glucose limitation) correlated well with the expression level of the ATP dependent pyruvate carboxylase and with the expression level of biotin synthase which provides the cofactor biotin for the formation of oxaloacetate from pyruvate. Bioenergetic analysis based on the formation rates of metabolites further show that ATP supply is not a limiting factor for the pyruvate carboxylation to oxaloacetate.ConclusionsThe results of physiological and proteomic analyses clearly show that the anaplerotic synthesis of oxaloacetate plays a key role in determining the growth behaviour of C. pasteurianum in fermentations with mixed substrates of glucose and glycerol. This study provides interesting targets for metabolic engineering of this emerging industrial microorganism.Electronic supplementary materialThe online version of this article (doi:10.1186/s12934-016-0497-4) contains supplementary material, which is available to authorized users.

Revalorization of strawberry surpluses by bio-transforming its glucose content into gluconic acid

Modern societies produce massive surpluses of food, by-products and wastes that increase the interest for their revalorization. This work examines the use of a culture of Gluconobacter japonicus CECT 8443, without pH control, to convert selectively the glucose content of industrially pasteurized strawberry purée into gluconic acid for the development of new beverages. However, depending on the initial concentration of glucose, the microorganism could transform the acid formed into other compounds; for this reason, in this work the effect of initial sugar concentration on the preservation of the acid was investigated. The results show that the gluconic acid formed in strawberry purée containing no added sugars started to disappear after glucose depletion, but the acid concentration remained constant if sugar-enriched purée was used. The use of this industrial substrate resulted in the presence of yeasts and hence in some fructose uptake; however, the fructose consumption was negligible until after 20–30h. The use of food by-products is an excellent opportunity not only to recover valuable compounds but for the development of new chemical and biotechnological approaches for their revalorization. This strategy should improve regional economies and contribute to a sustainable management of these underexploited resources.

Rhodosporidium toruloides cultivated in NaCl-enriched glucose-based media: Adaptation dynamics and lipid production.

In the present report and for the first time in the international literature, the impact of the addition of NaCl upon growth and lipid production on the oleaginous yeast Rhodosporidium toruloides was studied. Moreover, equally for first time, lipid production by R. toruloides was performed under nonaseptic conditions. Therefore, the potentiality of R. toruloides DSM 4444 to produce lipid in media containing several initial concentrations of NaCl with glucose employed as carbon source was studied. Preliminary batch-flask trials with increasing amounts of NaCl revealed the tolerance of the strain against NaCl content up to 6.0% w/v. However, 4.0% w/v of NaCl stimulated lipid accumulation for this strain, by enhancing lipid production up to 71.3% w/w per dry cell weight. The same amount of NaCl was employed in pasteurized batch-flask cultures in order to investigate the role of the salt as bacterial inhibiting agent. The combination of NaCl and high glucose concentrations was found to satisfactorily suppress bacterial contamination of R. toruloides cultures under these conditions. Batch-bioreactor trials of the yeast in the same media with high glucose content (up to 150 g/L) resulted in satisfactory substrate assimilation, with almost linear kinetic profile for lipid production, regardless of the initial glucose concentration imposed. Finally, fed-batch bioreactor cultures led to the production of 37.2 g/L of biomass, accompanied by 64.5% w/w of lipid yield. Lipid yield per unit of glucose consumed received the very satisfactory value of 0.21 g/g, a value among the highest ones in the literature. The yeast lipid produced contained mainly oleic acid and to lesser extent palmitic and stearic acids, thus constituting a perfect starting material for "second generation" biodiesel.

Carbon material distribution and flux analysis under varying glucose concentrations in hydrogen-producing Clostridium tyrobutyricum JM1

Anaerobic glucose metabolism in hydrogen-producing Clostridium tyrobutyricum was investigated in batch culture with varying initial glucose concentrations (27.8–333.6mM). To understand the regulation of metabolism, the carbon material and reduction balances were applied to estimate the carbon flux distribution for the first time, and metabolic flux analysis (MFA) was used to provide qualitative information and guidance for effective metabolic design. The overall flux distribution suggested that C. tyrobutyricum metabolism has a high capacity for the production of butyrate and hydrogen at an initial glucose concentration of 222.4mM, with balanced activities of NADH and ATP.

Growth characteristics of freeze-tolerant baker's yeast Saccharomyces cerevisiae AFY in aerobic batch culture.

Saccharomyces cerevisiae AFY is a novel baker’s yeast strain with strong freeze-tolerance, and can be used for frozen-dough processing. The present study armed to clarify the growth characteristics of the yeast AFY. Aerobic batch culture experiments of yeast AFY were carried out using media with various initial glucose concentrations, and the culture process was analyzed kinetically. The growth of the yeast AFY exhibited a diauxic pattern with the first growth stage consuming glucose and the second growth stage consuming ethanol. The cell yield decreased with increasing initial glucose concentration in the first growth stage, and also decreased with increasing initial ethanol concentration in the second growth stage. In the initial glucose concentration range of 5.0–40.0 g/L, the simultaneous equations of Monod equation, Luedeking–Piret equation and pseudo-Luedeking–Piret equation could be used to describe the concentrations of cell, ethanol and glucose in either of the two exponential growth phases. At the initial glucose concentrations of 5.0, 10.0 and 40.0 g/L, the first exponential growth phase had a maximal specific cell growth rate of 0.52, 0.98 and 0.99 h−1, while the second exponential growth phase had a maximal specific cell growth rate of 0.11, 0.06 and 0.07 h−1, respectively. It was indicated that the efficiency of the yeast production could be improved by reducing the ethanol production in the first growth stage.

Nitrogen and carbon source balance determines longevity, independently of fermentative or respiratory metabolism in the yeast Saccharomyces cerevisiae.

Dietary regimens have proven to delay aging and age-associated diseases in several eukaryotic model organisms but the input of nutritional balance to longevity regulation is still poorly understood. Here, we present data on the role of single carbon and nitrogen sources and their interplay in yeast longevity. Data demonstrate that ammonium, a rich nitrogen source, decreases chronological life span (CLS) of the prototrophic Saccharomyces cerevisiae strain PYCC 4072 in a concentration-dependent manner and, accordingly, that CLS can be extended through ammonium restriction, even in conditions of initial glucose abundance. We further show that CLS extension depends on initial ammonium and glucose concentrations in the growth medium, as long as other nutrients are not limiting. Glutamine, another rich nitrogen source, induced CLS shortening similarly to ammonium, but this effect was not observed with the poor nitrogen source urea. Ammonium decreased yeast CLS independently of the metabolic process activated during aging, either respiration or fermentation, and induced replication stress inhibiting a proper cell cycle arrest in G0/G1 phase. The present results shade new light on the nutritional equilibrium as a key factor on cell longevity and may contribute for the definition of interventions to promote life span and healthy aging.

Achieving High Yield of Lactic Acid for Antimicrobial Characterization in Cephalosporin-Resistant Lactobacillus by the Co-Expression of the Phosphofructokinase and Glucokinase.

Lactobacilli are universally recognized as probiotics that are widely used in the adjuvant treatment of inflammatory diseases, such as vaginitis and enteritis. With the overuse of antibiotics in recent years, the lactobacilli in the human body are killed, which could disrupt the microecological balance in the human body and affect health adversely. In this work, cephalosporin-resistant Lactobacillus casei RL20 was obtained successfully from the feces of healthy volunteers, which possessed a stable genetic set. However, the shortage of lactic acid (72.0 g/l at 48 h) by fermentation did not meet the requirement for its use in medicine. To increase the production of lactic acid, the functional genes pfk and glk were introduced into the wild strain. A yield of 144.2 g/l lactic acid was obtained in the transgenic L. casei RL20-2 after fermentation for 48 h in 1 L of basic fermentation medium with an initial glucose concentration of 100 g/l and increasing antibacterial activity. These data suggested that L. casei RL20-2 that exhibited a high yield of lactic acid may be a potential probiotic to inhibit the spread of bacterial infectious diseases and may be used for vaginitis therapy.

Use of response surface method for maximizing the production of arginine deiminase by Pseudomonas putida

Statistically designed experiments were used to optimize the production of arginine deiminase (ADI) by Pseudomonas putida KT2440 in batch culture. A Plackett-Burman design involving eleven factors showed that ADI production was most influenced by the initial pH and the initial concentrations of glucose and yeast extract. A central composite experimental design showed that the optimal values of these factors were 8.0, 10g/L and 12.5g/L, respectively. The other components of the optimal culture medium were bacto peptone 7.5g/L, Triton X–100 0.30% (v/v), and arginine 3g/L, for a culture temperature of 25°C. Compared with the basal medium, the ADI activity in the optimized medium had nearly 4.5-fold increase (4.31U/mL). The optimized medium was then used for a further study of ADI production in a 14L stirred tank bioreactor. The agitation speed and the aeration rates were varied to determine suitable values of these variables.

Dark fermentative hydrogen production by anaerobic sludge growing on glucose and ammonium resulting from nitrate electroreduction

The main objective of this work was to study the feasibility of biohydrogen production by heat-treated anaerobic sludge with glucose as carbon substrate and ammonium as nitrogen source, obtained from the electrochemical reduction of concentrated nitrate solutions (3 g L−1NO3−), namely model solutions simulating those obtained after physicochemical denitrification of industrial wastewaters. Experiments were realized in bacth systems involving 125 mL (without pH control) and 3 L (with pH control) reactor, respectively.In order to find the optimal conditions for H2 production, the first set of experiments were conducted without pH control at various initial pH (pH 5.5, 6.5 and 7.5) and glucose concentrations (5–30 g L−1); and the highest H2 yield (1.1 mol H2mol−1glucoseconsumed) was reached for a glucose concentration of 25 g L−1 and at pH 6.5. These optimal conditions were then considered to examine the effect of pH control on biohydrogen production, in a 3 L bioreactor. The pH control allowed a considerable improvement of the hydrogen gas conversion efficiency, which reached 2.02 mol H2mol−1glucoseconsumed.