Role of glutamine synthetase in citric acid fermentation byAspergillus niger

The activity of glutamine synthetase fromAspergillus niger was significantly lowered under conditions of citric acid fermentation. The intracellular pH of the organism as determined by bromophenol blue dye distribution and fluorescein diacetate uptake methods was relatively constant between 6•0–6•5, when the pH of the external medium was varied between 2•3–7•0.Aspergillus niger glutamine synthetase was rapidly inactivated under acidic pH conditions and Mn2+ ions partially protected the enzyme against this inactivation. Mn2+-dependent glutamine synthetase activity was higher at acidic pH (6•0) compared to Mg2+-supported activity. While the concentration of Mg2+ required to optimally activate glutamine synthetase at pH 6•0 was very high (≥ 50 mM), Mn2+ was effective at 4 mM. Higher concentrations of Mn2+ were inhibitory. The inhibition of both Mn2+ and Mg2+-dependent reactions by citrate, 2-oxoglutarate and ATP were probably due to their ability to chelate divalent ions rather than as regulatory molecules. This suggestion was supported by the observation that a metal ion chelator, EDTA also produced similar effects. Of the end-products of the pathway, only histidine, carbamyl phosphate, AMP and ADP inhibitedAspergillus niger glutamine synthetase. The inhibitions were more pronounced when Mn2+ was the metal ion activator and greater inhibition was observed at lower pH values. These results permit us to postulate that glutamine synthesis may be markedly inhibited when the fungus is grown under conditions suitable for citric acid production and this block may result in delinking carbon and nitrogen metabolism leading to acidogenesis.

Hydrogen production characteristics of the organic fraction of municipal solid wastes by anaerobic mixed culture fermentation

The hydrogen production from the organic fraction of municipal solid waste (OFMSW) by anaerobic mixed culture fermentation was investigated using batch experiments at 37 degrees C. Seven varieties of typical individual components of OFMSW including rice, potato, lettuce, lean meat, oil, fat and banyan leaves were selected to estimate the hydrogen production potential. Experimental results showed that the boiling treated anaerobic sludge was effective mixed inoculum for fermentative hydrogen production from OFMSW. Mechanism of fermentative hydrogen production indicates that, among the OFMSW, carbohydrates is the most optimal substrate for fermentative hydrogen production compared with proteins, lipids and lignocelluloses. This conclusion was also substantiated by experimental results of this study. The hydrogen production potentials of rice, potato and lettuce were 134 mL/g-VS, 106 mL/g-VS, and 50 mL/g-VS respectively. The hydrogen percentages of the total gas produced from rice, potato and lettuce were 57-70%, 41-55% and 37-67%. 2008 International Association for Hydrogen Energy.

Mixed culture fermentation studies on the effects of synbiotics on the human intestinal pathogens Campylobacter jejuni and Escherichia coli

Batch and continuous culture anaerobic fermentation systems, inoculated with human faeces, were utilised to investigate the antimicrobial actions of two probiotics, Lactobacillus plantartan 0407, combined with oligofructose and Bifidobacterium bifidum Bb12, combined with a mixture of oligofructose and xylo-oligosaccharides (50:50 w/w) against E coli and Campylobacter jejuni. In batch fermenters, both E coli and C jejuni were inhibited by the synbiotics, even when the culture pH was maintained at around neutral. In continuous culture C jejuni was inhibited but the synbiotic failed to inhibit E coli. Although no definitive answer in addressing the mechanisms underlying antimicrobial activity was derived, results suggested that acetate and lactate directly were conferring antagonistic action, rather than as a result of lowering culture pH. In the course of the study culturing and fluorescent in situ hybridisation (FISH) methodologies for the enumeration of bacterial populations were compared. Bifidobacterial populations were underestimated using plating techniques, suggesting the non-culturability of certain bifidobacterial species. (C) 2003 Elsevier Ltd. All rights reserved.

Mixed culture fermentation studies on the effects of synbiotics on the human intestinal pathogens Campylobacter jejuni and Escherichia coli

Batch and continuous culture anaerobic fermentation systems, inoculated with human faeces, were utilised to investigate the antimicrobial actions of two probiotics, Lactobacillus plantartan 0407, combined with oligofructose and Bifidobacterium bifidum Bb12, combined with a mixture of oligofructose and xylo-oligosaccharides (50:50 w/w) against E coli and Campylobacter jejuni. In batch fermenters, both E coli and C jejuni were inhibited by the synbiotics, even when the culture pH was maintained at around neutral. In continuous culture C jejuni was inhibited but the synbiotic failed to inhibit E coli. Although no definitive answer in addressing the mechanisms underlying antimicrobial activity was derived, results suggested that acetate and lactate directly were conferring antagonistic action, rather than as a result of lowering culture pH. In the course of the study culturing and fluorescent in situ hybridisation (FISH) methodologies for the enumeration of bacterial populations were compared. Bifidobacterial populations were underestimated using plating techniques, suggesting the non-culturability of certain bifidobacterial species. (C) 2003 Elsevier Ltd. All rights reserved.

Aerobic cultivation of Streptococcus zooepidemicus and the role of NADH oxidase

A metabolic flux model was developed for Streptococcus zooepidemicus to compare the metabolism of glucose and maltose during aerobic batch cultivation. Lactic acid was the main product of glucose metabolism whereas acetic acid was the main product of maltose metabolism. This difference was chiefly attributed to the two-fold higher flux through NADH oxidase in maltose-grown cells that enabled the ATP generation rate to remain high despite a slower maltose consumption rate. The two-fold higher flux was matched by a two-fold increase in NADH oxidase activity, 2.53 +/- 0.1 mumol NADH min(-1) mg(-1) protein on maltose versus 1.07 +/- 0.04 Rmol NADH min(-1) mg(-1) protein on glucose, indicating that NADH oxidase activity is regulated by the energy status of the cell. Surprisingly, the energy status of the cell had little impact on hyaluronic acid (HA) yield and molecular weight. (C) 2003 Elsevier Science B.V. All rights reserved.

Direct fermentation of potato starch wastewater to lactic acid by Rhizopus oryzae and Rhizopus arrhizus

The biochemical kinetic of direct fermentation for lactic acid production by fungal species of Rhizopus arrhizus 3,6017 and Rhizopus oryzae 2,062 was studied with respect to growth pH, temperature and substrate. The direct fermentation was characterized by starch hydrolysis, accumulation of reducing sugar, and production of lactic acid and fungal biomass. Starch hydrolysis, reducing sugar accumulation, biomass formation and lactic acid production were affected with the variations in pH, temperature, and starch source and concentration. A growth condition with starch concentration approximately 20 g/l at pH 6.0 and 30 degrees C was favourable for both starch saccharification and lactic acid fermentation, resulting in lactic acid yield of 0.87-0.97 g/g starch associated with 1.5-2.0 g/l fungal biomass produced in 36 h fermentation. R. arrhizus 3,6017 had a higher capacity to produce lactic acid, while R. oryzae 2,062 produced more fungal biomass under similar conditions.

Simultaneous saccharification and fermentation of potato starch wastewater to lactic acid by Rhizopus oryzae and Rhizopus arrhizus

The biochemical kinetic of simultaneous saccharification and fermentation (SSF) for lactic acid production by fungal species of Rhizopus arrhizus 36017 and Rhizopus oryzae 2062 was studied with respect to growth pH, temperature and substrate. Both R. arrhizus 36017 and R. oryzae 2062 had a capacity to carry out a single stage SSF process for lactic acid production from potato starch wastewater. The kinetic characteristics, termed as starch hydrolysis, accumulation of reducing sugars, lactic acid production and fungal biomass formation, were affected with variations in pH, temperature, and starch source and concentration. A growth condition with starch concentration approximately 20 g/l at pH 6.0 and 30 degrees C was favourable for both starch saccharification and lactic acid fermentation, resulting in lactic acid yield of 0.85-0.92 g/g associated with 1.5-3.5 g/l fungal biomass produced in 36-48 h fermentation. R. arrhizus 36017 had a higher capacity to produce lactic acid, while R. oryzae 2062 produced more fungal biomass under similar conditions. (c) 2005 Elsevier B.V. All rights reserved.

The Use of Response Surface Methodology in Optimization of Lactic Acid Production: Focus on Medium Supplementation, Temperature and pH Control

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Kinetic studies on clavulanic acid degradation

Clavulanic acid (CA), a potent beta-lactamase inhibitor, is very sensitive to pH and temperature. It is produced by Streptomyces clavuligerus and to optimize both the fermentation step and the downstream process, the expression of the hydrolysis kinetics has to be determined. In the present work the CA degradation rate from various sources was investigated at temperatures of 10, 20, 25, 30 and 40degreesC and PH values of 6.2 and 7.0. The results showed that first-order kinetics explained very well the hydrolysis kinetics and the Arrhenius equation could be applied to establish a relationship between the degradation rate constant and temperature, at both pHs. It has been observed that CA from fermentation medium was much more unstable than that from standard solution and from a commercially available medicine. Also, it was observed that CA was more stable at PH 6.2 than at pH 7.0, irrespective of the CA source. (C) 2004 Elsevier B.V. All rights reserved.

L(+) Lactic acid production by new Lactobacillus rhamnosus B 103

L(+) Lactic acid fermentation was studied by Lactobacillus rhamnosus sp. under the effects of pH control and a lowcost nutritional medium (sugarcane juice and corn steep liquor-CSL). Central composite design (CCD) was employed to determine maximum lactic acid production at optimum values for process variables and a satisfactory fit model was realized. Statistical analysis of the results showed that the linear and quadratic terms of two variables (sugarcane juice and pH) had significant effects. The interactions between the three variables were found to contribute to the response at a significant level. A second-order polynomial regression model estimated that the maximum lactic acid production of 86.36 g/L was obtained when the optimum values of sucrose, CSL and pH were 112.65 g/L, 29.88 g/L and 6.2, respectively. Verification of the optimization showed that L(+) lactic acid production was of 85.06 g/L. Under these conditions, Y P/S and Q P values of 0.85 g/g and 1.77 g/Lh, respectively, were obtained after 48 h fermentation, with a maximal productivity of 2.2 g/L h at 30 h of process. © 2010 de Lima CJB, et al.

Pilot plant for production of fish ensilage and the economics of production

This communication describes the design aspect and functions of individual pieces of equipment of a pilot plant for the production of fish ensilage based on lactic acid fermentation process. Details about the equipment, process flow sheet and equipment layout of the pilot plant have been given. An attempt has been made to prepare an estimate of the cost of production of liquid ensilage and solid feed mix.

Major, minor and trace-elemental contents analysis in northeast soybeans by ICP-AES

Major, minor and trace elemental contents in northeast China soybeans were determined by using inductively, coupled plasma atomic emission spectrometry (ICP-AES). Three different sample digestion methods including two wet digestions, HNO3-HClO4 and HNO3-H2SO4 and a dry ash method were compared. Owing to the high oil content in soybeans, long time is needed and access acid should be added, with mixed acid digestion methods, which may result in higher sample blank. Therefore, the dry ask method would be more proper for the pre-treatment of soybean samples. Potassium and phosphorus are major elements in soybeans, so the effect of potassium and phosphorus on the other elements was investigated. Results showed that the potassium and phosphorus did not affect the determination. of other trace elements. There are not significant differences in trace elemental contents for the eleven northeast China soybeans.

Lu-Hf同位素的MC-ICP-MS实验方法及其在华北克拉通典型火山岩研究中的应用

Over past ten years, a great development has been made in the Lu-Hf isotopic system with the advent of MC-ICP-MS. Based on a comprehensive review of available references in the related field, a novel analytical protocol of three exchange chromatographies after one mixed acid attacking geological samples was developed in this work, which not only avoids common multiple sample treatments for natural inhomegeneous samples, but also is useful for Rb-Sr, Sm-Nd and Lu-Hf isotopic system simultaneously, especially for the garnet- and apatite-bearing rocks for the Sm-Nd and Lu-Hf geochronology. An analytical procedure for the Lu and Hf concentration in geological samples determined by by ID-MC-ICP-MS was detailedly investigated. The Hf yield is > 90 % and total procedural blank is less than. 50 pg for Hf and 10 pg for Lu, respectively. The developed method was successfully applied to the determination of Lu and Hf concentrations for USGS geological materials. A one-column procedure for Hf purification in geological samples using common anion exchange chromatography and its isotopic analyses by MC-ICP-MS were also established. Multiple analyses of Standard Reference Materials demonstrate that this method was simple, time-saving, cheap and efficient, especially suitable for the Hf isotopic compositions of young samples. Finally, the measurements of Sr and Nd isotopic compositions using Neptune MC-ICP-MS were described briefly, which indicates that Neptune MC-ICP-MS can precisely measure Sr and Nd isotopic compositions as the TIMS does, even more efficient and less time-consuming than the TIMS method. The Hf isotopic characteristics of typical volcanic rocks (Cenozoic Changle-Linqu basalts, Mesozoic Fangcheng basalts, Mesozoic Jianguo basalts, Mesozoic Wulahada high-Mg andesite, Cenozoic Fanshi, Zuoquan and Xiyang-Pingding basalts of the Taihang Mountains, Paleozoic diamondiferous Menyin and Fuxian Kimblites) from the North China Craton were firstly studied in this work. Coupled with Nd isotopic compositions, it shows that the Hf isotopes could be a better tracer for mantle sources than the Nd isotopes. Individual kimberlite fields from both the Mengyin and Fuxian regions have quite uniform Hf isotopic compositions, similar to the situation for the Nd isotopes.

Produção de amido modificado de mandioca com propriedade de expansão

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)