Synthetic Glucose Medium Research Articles

Properties of cellulose nitrates produced by nitration of bacterial cellulose using mixed sulfuric-nitric acids

The study set out to investigate the chemical functionalization of bacterial cellulose as an alternative means of satisfying the high demand for nano-sized cellulose nitrates. Using a Medusomyces gisevii Sa-12 symbiotic culture as a microbial producer, bacterial cellulose having a polymerization degree of 3950 was obtained on a synthetic glucose medium. Nitration was carried out using mixed sulfuric-nitric acids differing in their water content, followed by stabilization of the synthesized bacterial cellulose nitrates. Subject to a varying water content (14, 16 and 20 %) in the nitrating mixture, the obtained bacterial cellulose nitrates exhibited a nitrogen mass content of 8.68–11.56 %, a solubility in alcohol-ether mixture of 16.5–91.0 % and a viscosity of 32–255 mPa×s. The bacterial cellulose nitrate fibers were shown to have a nanoscale nature. Coupled thermogravimetric and differential thermal analyses revealed the bacterial cellulose nitrates to have a high chemical purity and energy content. FTIR spectroscopy confirmed the high quality of the bacterial cellulose based on the presence of basic functional groups characteristic of conventional cellulose: 3371, 2943, 1633, 1428, 1371, 1163, and 1112 cm-1. According to their infrared spectra, the detected basic functional groups corroborate that the synthesized products are low-substituted cellulose nitrate esters: 1660–1643, 1282-1276, 847–837, 752–749, and 691–690 cm-1. The relationship between the properties of the synthesized bacterial cellulose nitrates and the water mass content in mixed sulfuric-nitric acids is shown to have a complex nature.

Isolation, characterization, and genome assembly of Barnettozyma botsteinii sp. nov. and novel strains of Kurtzmaniella quercitrusa isolated from the intestinal tract of the termite Macrotermes bellicosus.

Bioconversion of hemicelluloses into simpler sugars leads to the production of a significant amount of pentose sugars, such as d-xylose. However, efficient utilization of pentoses by conventional yeast production strains remains challenging. Wild yeast strains can provide new industrially relevant characteristics and efficiently utilize pentose sugars. To explore this strategy, we isolated gut-residing yeasts from the termite Macrotermes bellicosus collected in Comoé National Park, Côte d’Ivoire. The yeasts were classified through their Internal Transcribed Spacer/Large Subunit sequence, and their genomes were sequenced and annotated. We identified a novel yeast species, which we name Barnettozyma botsteinii sp. nov. 1118T (MycoBank: 833563, CBS 16679T and IBT 710) and two new strains of Kurtzmaniella quercitrusa: var. comoensis (CBS 16678, IBT 709) and var. filamentosus (CBS 16680, IBT 711). The two K. quercitrusa strains grow 15% faster on synthetic glucose medium than Saccharomyces cerevisiae CEN.PKT in acidic conditions (pH = 3.2) and both strains grow on d-xylose as the sole carbon source at a rate of 0.35 h−1. At neutral pH, the yeast form of K. quercitrusa var. filamentosus, but not var. comoensis, switched to filamentous growth in a carbon source-dependent manner. Their genomes are 11.0–13.2 Mb in size and contain between 4888 and 5475 predicted genes. Together with closely related species, we did not find any relationship between gene content and ability to grow on xylose. Besides its metabolism, K. quercitrusa var. filamentosus has a large potential as a production organism, because of its capacity to grow at low pH and to undergo a dimorphic shift.

Bioconversions of olive oil mill wastewaters blends

<p>The ability of the anaerobic mixed bacterial culture from an upflow anaerobic sludge blanket (UASB) bioreactor to convert blends of olive mill wastewaters (OMWs) with synthetic glucose medium or molasses into ethanol simultaneously with organic acids (OAs) was studied in the present work. All fermentations were conducted by free cells under non-aerated conditions at 37 οC and the effect of OMWs concentration on ethanol and OAs production was investigated. The highest amount of bioethanol (14.7 g L-1) was produced during fermentation of 45 % v/v OMWs mixed with synthetic glucose medium (5 % w/v) in only 28 hours. In mixtures of 30 % v/v OMWs and molasses solution (3 oBe) 13.4 g L-1 of bioethanol were produced. Also, 16.2 g L-1 of succinic acid were produced, when 65 % v/v OMWs mixed with synthetic glucose medium. Moreover, totally 11.6 g L-1 of varied OAs (succinic, malic, butyric and acetic) observed in mixtures of 35 % OMWs with molasses. Finally, it has been shown that the 14C-labelled glucose uptake rate (GUR) by biomass was strongly correlated to fermentation rate.</p>

γ-Alumina as a process advancing tool for a new generation biofuel

The production of volatile fatty acids (VFAs) in a continuous process using a synthetic glucose medium as model substrate in the presence of γ-alumina as promoter is described. The results showed formation of acetic, propionic, isobutyric, butyric, isovaleric and valeric acids, with acetic acid being more than 90% of the total VFAs produced. It is also highlighted that γ-alumina enhanced the simultaneous production of acetic acid and ethanol, which in some cases was formed at concentrations able to esterify about 85% of the produced VFAs. Since most agro-industrial effluents can be treated by anaerobic acidogenic digestion, while lignocellulosic biomass can be converted to VFAs after hydrolysis, this contribution can lead to a breakthrough in the research of biofuel production from renewable waste sources.

The Production of Nata Colored by Monascus purpureus J1 Pigments as Functional Food

Pigments from Monascus sp. may color nata. The mold also produces monacolin K that inhibits HMG-CoA reductase affecting the reduction of blood cholesterol. The aim of this study was to produce the colored nata containing monacolin K. The mold was isolated from commercial angkak. Potato sucrose (PS) and synthetic glucose (SG) media were used to ferment nata with Monascus purpureus J1. Fermentation of nata in PS medium produced red nata, while that in SG medium produced orange nata. The color of nata was similar to the color of supernatant. The optimum red production was obtained after five days of incubation, while the orange production increased until the 14 th day. The color concentrations of the supernatant of PS medium containing nata (35.4 μg mL -1 ) were lower than those without nata (12.4 μg mL -1 ). The colors of nata looked darker than the color of the supernatant. The concentration of monacolin K in the red nata and the supernatant of PS medium were 0.6 μg mL-1 and 4.6 μg mL -1 respectively, while those in the orange nata and the supernatant of SG medium were 3.2 μg mL -1 and 14.6 μg mL -1 respectively. Dry matter biomass in the PS medium was lower than that in the SG medium. Even though the color of nata looked relatively stable, analyses of the nata water extract that showed a stable condition only occurred in freezing (-20 O C) and soaking in buffer solution of pH 12; boiling, water washing, and soaking in a solution of pH 3 and 7 reduced the pigment concentration. Monacolin K concentration was not stable for every treatment, especially for water washing and freezing. Eventhough it was not stable, the boiling nata contained red pigments and monacolin K of 19.7 μg mL -1 and 0.1 μg mL -1 respectively, which can be served as functional food.

Quantitative analysis of methanogenic community dynamics in three anaerobic batch digesters treating different wastewaters

Quantitative changes in methanogenic community structures, associated with performance data, were investigated in three anaerobic batch digesters treating synthetic glucose medium, whey permeate, and liquefied sewage sludge. All digesters were initially seeded with anaerobic sludge obtained from a local municipal wastewater treatment plant. Dynamics of methanogenic populations were monitored, at order and family levels, using real-time PCR based on the 16S rRNA gene. The molecular monitoring revealed that, in each digester, the quantitative structure of methanogenic community varied continuously over treatment time and the variation corresponded well to the changes in chemical profiles. Biphasic production of methane, associated with successive increases in aceticlastic (mainly Methanosarcinaceae) and hydrogenotrophic (mainly Methanomicrobiales) methanogenic groups, was observed in each digester. This corresponded to the diauxic utilization of acetate and longer-chain volatile fatty acids (C 3–C 6), mainly propionate. Additionally, the non-metric multidimensional scaling (NMDS) analysis of the quantification results demonstrated that the community shift patterns in three digesters were totally different from each other. Considering that the operating conditions in all trials were identical except substrates, the differences in quantitative shift profiles were suggested to be due to the different substrate compositions. This implied that the composition of wastewater could affect the evolution of quantitative methanogenic community structure in an anaerobic process. Overall, our results suggested that more attention to quantitative as well as qualitative approaches on microbial communities is needed for fundamental understanding of anaerobic processes, particularly under dynamic or transitional conditions.

Novel Structure of the N Terminus in Yeast Fis1 Correlates with a Specialized Function in Mitochondrial Fission

Mitochondrial fission is facilitated by a multiprotein complex assembled at the division site. The required components of the fission machinery in Saccharomyces cerevisiae include Dnm1, Fis1, and Mdv1. In the present study, we determined the protein structure of yeast Fis1 using NMR spectroscopy. Although the six alpha-helices, as well as their folding, in the yeast Fis1 structure are similar to those of the tetratricopeptide repeat (TPR) domains of the human Fis1 structure, the two structures differ in their N termini. The N-terminal tail of human Fis1 is flexible and unstructured, whereas a major segment of the longer N terminus of yeast Fis1 is fixed to the concave face formed by the six alpha-helices in the TPR domains. To investigate the role of the fixed N terminus, exogenous Fis1 was expressed in yeast lacking the endogenous protein. Expression of yeast Fis1 protein rescued mitochondrial fission in delta fis1 yeast only when the N-terminal TPR binding segment was left intact. The presence of this segment is also correlated to the recruitment of Mdv1 to mitochondria. The conformation of the N-terminal segment embedded in the TPR pocket indicates an intra-molecular regulation of Fis1 bioactivity. Although the TPR-like helix bundle of Fis1 mediates the interaction with Dnm1 and Mdv1, the N terminus of Fis1 is a prerequisite to recruit Mdv1 to facilitate mitochondrial fission.

Development of a biosensor for the detection of tributyltin.

A biosensor (LUMISENS I), based on the inducible bioluminescence of the Escherichia coli strain TBT3 (Ec::luxAB TBT3), was developed for the detection of the biocide tributyltin. LUMISENS I was set up with a minibioreactor and additional equipment for growth monitoring and light acquisition. The 100-mL minibioreactor has allowed us to establish a stable and reproducible environment for the bacteria (regulation of the growth rate, temperature, pH, and oxygenation), as well as for in situ contact with the xenobiotic. The optical components of the transducer were chosen according to the spectral emission of the strain being studied using a highly sensitive spectrophotometer that was initially devoted to Raman scattering. LUMISENS I was patented according to the in situ, automatic, and simultaneous measurement of the cell density and bioluminescence in the bioreactor. The first results showed that cells cultivated in a synthetic glucose medium provided a better detection limit than did those cultivated in a complex Luria-Bertani (LB) medium (0.02 and 1.5 microM of tributyltin, respectively). Cells maintained at a high growth rate (0.9 h(-1)) led to maximum bioluminescence. Moreover, air bubbling was efficient enough to provide suitable quantities of oxygen for both growth and light emission. When the TBT3 strain used the luxAB genes on its own, decanal, a long-chain aldehyde, had to be added to obtain the bioluminescence reaction. We found that the continuous addition of decanal was the most effective means of obtaining this reaction. The monitoring of the bioluminescence after tributyltin induction showed that the aldehyde was not toxic up to 300 microM during a 7-day experiment. Measurement of tributyltin with LUMISENS I was performed, which showed significant response up to 0.125 microM without any effect on optical density. Even though optimization of the performance of LUMISENS I is still under development, because of its original design, this biosensor is already in use as a warning system for the online monitoring of tributyltin.

Development of a biosensor for on-line detection of tributyltin with a recombinant bioluminescent Escherichia coli strain.

A biosensor was developed for the detection of tributyltin (TBT), using a bioluminescent recombinant Escherichia coli:: luxAB strain. Dedicated devices allowed the on-line measurement of bioluminescence, pH and dissolved oxygen values and the feed-back regulation of temperature. Bacterial physiology was monitored by the measurement of the cellular density, respiratory activity and the intracellular level of ATP, glucose and acetate levels. Our results showed that a synthetic glucose medium gave a better TBT detection limit than LB medium (respectively 0.02 micro M and 1.5 micro M TBT). High growth and dilution rates ( D=0.9 h(-1)) allowed maximum light emission from the bacterium. Moreover, simple atmospheric air bubbling was sufficient to provide oxygen for growth and the bioluminescence reaction. Real-time monitoring of bioluminescence after TBT induction occurred with continuous addition of decanal up to 300 micro M, which was not toxic throughout a 7-day experiment. The design of our biosensor and the optimization of the main parameters that influence microbial activity led to the capacity for the detection of TBT.

Yeast Lacking Cu-Zn Superoxide Dismutase Show Altered Iron Homeostasis: ROLE OF OXIDATIVE STRESS IN IRON METABOLISM

Saccharomyces cerevisiae lacking copper-zinc superoxide dismutase (sod1) shows a series of defects, including reduced rates of aerobic growth in synthetic glucose medium and reduced ability to grow by respiration in glycerol-rich medium. In this work, we observed that addition of iron improved the respiratory growth of the sod1 mutant and in glucose medium total intracellular iron content was higher in the sod1 mutant than in wild type cells. Transcription of the high affinity iron transporter gene, FET3, was enhanced in the sod1 mutant, suggesting that iron transport systems were up-regulated. An sod1/fet3 double mutant showed increased sensitivity to oxygen and increased transcription of FET4, an alternative, low affinity, iron transporter. We propose that this increased iron demand in the sod1 mutant may be a reflection of the cells' efforts to reconstitute iron-sulfur cluster-containing enzymes that are continuously inactivated in conditions of excess superoxide.

Insulin signaling in the yeast Saccharomyces cerevisiae. 1. Stimulation of glucose metabolism and Snf1 kinase by human insulin.

Effects of human insulin on glucose metabolism in the yeast Saccharomyces cerevisiae were studied in this report. Under two conditions of growth limitation (glucose-grown cells during transition to stationary phase or spheroplasts during incubation in synthetic glucose medium), human insulin (10 and 1 microM, respectively) enhanced glycogen accumulation and glycogen synthase activity by 40-60% compared to control cells. Glycogen phosphorylase activity was also increased under the same conditions, but this stimulation was diminished by 35-45% in insulin-treated compared to control cells. Thus, under growth limitation, insulin causes glycogen phosphorylase and glycogen synthase to become more sensitive to inactivation and activation, respectively. In glucose-induced spheroplasts, insulin (1 microM), in addition to glycogen accumulation, led to about 2-fold increases of the rates of ethanol production and glucose oxidation compared to control cells, and the maximal concentration of hexose 6-phosphate was increased by 30-40%. In contrast, glucose transport as well as the levels of the allosteric regulators, fructose 2,6-bisphosphate and cAMP, were not altered at all. Snf1 kinase is assumed to be involved in the regulation of glycogen metabolism in yeast, although it does not seem to be modulated directly by the glucose concentration. Snf1 kinase activity was elevated 5-10-fold in response to insulin both during glucose induction of yeast spheroplasts and during transition to stationary phase of glucose-grown cells. We conclude that Saccharomyces cerevisiae and insulin-sensitive mammalian cells share some parts of the signaling cascades regulating oxidative and nonoxidative glucose metabolism in response to glucose and insulin.

Optimization of cell yield of Candida krusei SO1 and Saccharomyces sp. LK3G cultured in sorghum hydrolysate

The fed-batch approach to the production of single-cell protein (SCP) from synthetic glucose medium or sorghum hydrolysate by Candida krusei SO1 and Saccharomyces sp. LK3G was studied in aerobic conditions. The results obtained with a synthetic glucose showed better growth parameters under fed-batch conditions than under batch conditions. Biomass yield ( Y x s ) was increased by as much as 64% for Candida krusei and for Saccharomyces sp. LK3G by as much as 70%. Volumetric cell productivity was also improved for both yeasts: 0.75 g/l.h in fed-batch conditions against 0.68 g/l.h in batch conditions for Candida krusei SO1 and 0.63 g/l.h against 0.56 g/l.h for Saccharomyces sp. LK3G. Chemical analyses of yeast cells grown on either synthetic medium or on sorghum hydrolysate showed that the fed-batch process did not alter the nutritional quality of either yeast strain: in these conditions their protein content (47–50%) and their amino acid profiles compared favourably with the Food and Agricultural Organization references. Furthermore, both yeast strains were good sources of mineral salts.

Isolation and physiological characterization of yeasts involved in sorghum beer production

Abstract Yeasts responsible for sorghum beer fermentation were isolated and their physiological characteristics were studied. Twelve typical strains were identified in six beers and found to belong to genera Candida and Saccharomyces. Batch cultures of Candida krusei SOI, Saccharomyces cerevisiae LT3L1, Saccharomyces sp. LK3G and Saccharomyces cerevisiae LT1L2 were carried out in a synthetic glucose medium. The maximum growth rate and cell yield were dependent on incubation temperature and degree of aeration. Optimum temperature of culture was 30°C for the four tested yeast strains. When grown on synthetic glucose medium and on natural sorghum medium they had a balanced amino acid profile, except for sulfur‐containing amino acids. Considering their protein contents and their amino acid profiles, Candida krusei SOI and Saccharomyces cerevisiae LT1L2 show some promise as an additive for human nutrition.

Production of butyric acid by batch fermentation of cheese whey withClostridium beijerinckii

The effect of pH on the fermentation of butyric acid byClostridium beijerinckii using cheese whey as a substrate was studied. Maximum concentrations of the acid were produced when the pH was controlled at 5.5. Raising or lowering of pH was found to reduce the total acid formation. This particular strain ofC. beijerinckii produced insignificant amounts of butanol in all the pure culture cases investigated. A comparative study of the fermentation in a synthetic glucose medium and in cheese whey showed the whey to produce more butyric acid.

Invertase and phosphatase of yeast in a phosphate-limited continuous culture

Deficiency of inorganic phosphate caused the hyper production of invertase and the derepression of acid phosphatase in a continuous culture ofSaccharomyces carlsbergensis. The specific invertase activity was 40,000 enzyme units per g dry cell weight at a dilution rate lower than 0.05 h−1 with a synthetic glucose medium of which the molecular ratio of KH2PO4 to glucose was less than 0.006. This activity is eight fold higher than in a batch growth and 1.5 fold as much as the highest enzyme activity observed so far in a glucose-limited continuous culture.

Physiological characterictics and energy balance ofKlebsiella aerogenes in a multistage tower fermentor

Biomass growth, consumption of carbon and energy source, specific rates of formation of metabolic byproducts, biomass yield referred to the C-source and to oxygen, respiration rate and the value of RQ were studied in Klebsiella aerogenes CCM 2318 (on a synthetic glucose medium) at different specific growth rates. Maintenance coefficients and the total energy balance of the cultivation process were evaluated for a multistage tower fermentor with a defined interstage mixing. The results pointed to changes in both glucose metabolism and the physiological state of the population, brought about by changes in specific growth rate. As compared with a chemostat, the culture was found to exhibit a different physiological character is stages 1 and 4 despite a considerable interstage mixing.

Soluble sugars in the mycelium of the basidiomycete Oudemansiella mucida.

Quantitative gas chromatography was used to determine soluble neutral sugars in an extract of the fungus Oudemansiella mucida grown on a synthetic glucose medium. Apart from the usual fungal sugar components, viz. trehalose, D-glucose, D-mannitol, D-arabinitol, glycerol and inositol, the 6-day-old mycelium contained D-arabino-2-hexosulose (D-glucosone). In the period of maximum growth, this aldoketose was the predominant monosaccharide (3.4% mycelial dry weight).

Effect of oxygen supply on growth ofKlebsiella aerogenes in a multistage tower fermentor

The effect of the rate of oxygen supply on biomass growth, consumption of carbon source formation of metabolic by-products, biomass yeilds referred to C-source and oxygen, respiration rate and the respiratory quotient was studied in a multistage tower fermentor with an interstage backflow, i.e. with a continuous reinoculation of the preceding stages. Experiments were done with Klebsiella aerogenes CCM 2318 in a synthetic glucose medium with constant glucose concentration in the feed, at pH 7.0. temperature 30 degrees C, and dilution rates 0.6 and 0.178 h-1 (referred to one stage). Different behavior of the culture was found at different dilution rates both with oxygen and under oxygen limitation. As compared with the chemostat system, the regime with an interstage backflow exhibited differences in respiration rate and CO2 formation; this attests to a considerably different physiological state of the cells.

Studies on the physiology and metabolism of hydrocarbon-utilizing microorganisms. XV. Effect of biotin on the level of isocitrate lyase in Candida tropicalis.

The level of isocitrate lyase, an enzyme of glyoxylate cycle, in Candida tropicalis was enhanced at the later period of growth when the yeast was cultivated in a semisynthetic glucose medium. On the other hand, such increase in the enzyme activity was not observed in C. lipolytica grown under the same conditions. In the case of C. tropicalis, high concentrations of glucose remaining in the medium permitted the increase in the enzyme activity and the addition of ethanol, one of the major products from glucose, to the glucose medium did not stimulate the enzyme formation, indicating that the enhanced enzyme level in the yeast was not merely attributable to the release from the repression by glucose or to the induction by ethanol. Biotin, one of the growth-stimulating factors for C. tropicalis, affected markedly the level of isocitrate lyase. That is, the supplementation of biotin to the synthetic glucose medium inhibited completely the increase in the enzyme activity, and reversely the absence of biotin sti...

Rhizomorph Formation in Fungi III. The Effect of Ethanol on the Synthesis of DNA and RNA and Uptake of Asparagine and Phosphate in Armillaria mellea

AbstractGrowth and rhizomorph formation in Armillaria mellea (Vahl ex Fr.) Quél. can be stimulated by ethanol when grown on a synthetic glucose medium. The content of DNA (deoxy‐ribonucleic acid) and RNA (ribonucleic acid) in cultures of A. mellea have been followed during a growth period in relation to growth (dry weight) and ethanol uptake with 3 different initial ethanol concentrations. The continuous increase in dry weight as well as DNA and RNA contents during growth showed similar exponential rates as long as ethanol was present in the medium. The final amounts were proportional to the initial ethanol concentration.A further supply of ethanol caused a similar proportional increase in dry weight and also in the DNA and RNA contents, which indicates that the growth stimulated by ethanol is caused by cell divisions rather than an accumulation of lipids or polysaccharides. Uptake of asparagine and phosphate were also stimulated by ethanol.