Kinetics of kojic acid fermentation byAspergillus flavus link S44-1 using sucrose as a carbon source under different pH conditions

Kojic acid production byAspergillus flavus strain S44-1 using sucrose as a carbon source was carried out in a 250-mL shake flask and a 2-L stirred tank fermenter. For comparison, production of kojic acid using glucose, fructose and its mixture was also carried out. Kojic acid production in shake flask fermentation was 25.8 g/L using glucose as the sole carbon source, 23.6 g/L with sucrose, and 6.4 g/L from fructose. Reduced kojic acid production (13.5 g/L) was observed when a combination of glucose and fructose was used as a carbon source. The highest production of kojic acid (40.2 g/L) was obtained from 150 g/L sucrose in a 2 L fermenter, while the lowest kojic acid production (10.3 g/L) was seen in fermentation using fructose as the sole carbon source. The experimental data from batch fermentation and resuspended cell system was analysed in order to form the basis for a kinetic model of the process. An unstructured model based on logistic and Luedeking-Piret equations was found suitable to describe the growth, substrate consumption, and efficiency of kojic acid production byA. flavus in batch fermentation using sucrose. From this model, it was found that kojic acid production byA. flavus was not a growth-associated process. Fermentation without pH control (from an initial culture pH of 3.0) showed higher kojic acid production than single-phase pH-controlled fermentation (pH 2.5, 2.75, and 3.0).     

Impact of beef extract and six carbon source on antifungal metabolites production by bacterium associated with entomopathogenic nematode against Fusarium oxysporum

A specific symbiotic Bacillus species isolated from a rhabditid entomopathogenic nematode, Rhabditis (Oscheius) sp., was found to produce a number of bioactive compounds. The present study was conducted to determine the effect of six different carbon sources in combination with beef extract on the production of antifungal substances by Bacillus sp. The yield of crude antimicrobial substances and antimicrobial activity against the test microorganism also differed significantly when the carbon sources in the fermentation media were changed. The highest yield was recorded for fructose plus beef extract (956?mg/l). The antifungal activity was significantly high in beef extract plus maltose (21?±?1.5?mm) followed by beef extract plus glucose and beef extract plus fructose. Antifungal activity was significantly reduced in beef extract plus lactose and sucrose. High pressure liquid chromatography analysis of the crude antimicrobial substances revealed different peaks with different retention times indicating that they produced different compounds. When a carbon source was not included in the fermentation media, the antifungal production was substantially reduced. Carbon source in the fermentation medium plays a vital role in the production of antimicrobial substances. Beef extract and maltose as nitrogen and carbon sources in the fermentation medium produced maximum antifungal activity. It is concluded that Beef extract and maltose as nitrogen and carbon sources produced maximum activity which can effectively control the Fusarium oxysporum which causes vascular fusarium wilt in tomato, tobacco, legumes, cucurbits, sweet potatoes, banana, etc.     

Substrate utilization by recombinant Yarrowia lipolytica growing on sucrose

We report the study of the dynamics of substrate utilization by the genetic modified strain Yarrowia lipolytica H222-S4(p67ICL1) T5. In contrast to its wild-type equivalent, this recombinant strain is able to excrete the sucrose cleaving enzyme invertase. Both the sucrose degradation rate and the glucose and fructose consumption rate have been investigated. In all experiments, satisfied amounts of invertase were produced so that all sucrose was cleaved into its monomers. While glucose and fructose as sole carbon sources were consumed with the same uptake rate, a clear preference for glucose uptake was detected in cultivations with sucrose as sole carbon source or mixed substrates when compared with fructose. Nevertheless, no real diauxie could be observed because of partly simultaneous consumption of both monosaccharides. Fructose being present in the cultivation medium at the beginning of the fermentation led to the retardation of glucose uptake. This effect was observed for various fructose starting concentrations in the range of 5–85 g/l.     

A novel methodology independent of fermentation rate for assessment of the fructophilic character of wine yeast strains

The yeast Saccharomyces cerevisiae has a fundamental role in fermenting grape juice to wine. During alcoholic fermentation its catabolic activity converts sugars (which in grape juice are a near equal ratio of glucose and fructose) and other grape compounds into ethanol, carbon dioxide and sensorily important metabolites. However, S. cerevisiae typically utilises glucose and fructose with different efficiency: glucose is preferred and is consumed at a higher rate than fructose. This results in an increasing difference between the concentrations of glucose and fructose during fermentation. In this study 20 commercially available strains were investigated to determine their relative abilities to utilise glucose and fructose. Parameters measured included fermentation duration and the kinetics of utilisation of fructose when supplied as sole carbon source or in an equimolar mix with glucose. The data were then analysed using mathematical calculations in an effort to identify fermentation attributes which were indicative of overall fructose utilisation and fermentation performance. Fermentation durations ranged from 74.6 to over 150 h, with clear differences in the degree to which glucose utilisation was preferential. Given this variability we sought to gain a more holistic indication of strain performance that was independent of fermentation rate and therefore utilized the area under the curve (AUC) of fermentation of individual or combined sugars. In this way it was possible to rank the 20 strains for their ability to consume fructose relative to glucose. Moreover, it was shown that fermentations performed in media containing fructose as sole carbon source did not predict the fructophilicity of strains in wine-like conditions (equimolar mixture of glucose and fructose). This work provides important information for programs which seek to generate strains that are faster or more reliable fermenters.     

Variation in the Nature of Organic Acid Secretion and Mineral Phosphate Solubilization by Citrobacter sp. DHRSS in the Presence of Different Sugars

A novel phosphate solubilizing bacterium (PSB) was isolated from the rhizosphere of sugarcane and is capable of utilizing sucrose and rock phosphate as the sole carbon and phosphate source, respectively. This PSB exhibited mineral phosphate solubilizing (MPS) phenotype on sugars such as sucrose and fructose, which are not substrates for enzyme glucose dehydrogenase (GDH), along with GDH substrates, viz., glucose, xylose, and maltose, as carbon sources. PCR amplification of the rRNA gene and sequence analysis identified this bacterium as Citrobacter sp. DHRSS. On sucrose and fructose Citrobacter sp. DHRSS liberated 170 and 100 μM free phosphate from rock phosphate and secreted 49 mM (2.94 g/L) and 35 mM (2.1 g/L) acetic acid, respectively. Growth of Citrobacter sp. DHRSS on sucrose is mediated by an intracellular inducible neutral invertase. Interestingly, in the presence of GDH substrates like glucose and maltose, Citrobacter sp. DHRSS produced approximately 20 mM (4.36 g/L) gluconic acid and phosphate released was 520 and 570 μM, respectively. Citrobacter sp. DHRSS GDH activity was found when grown on GDH and non-GDH substrates, indicating that it is constitutive and could act on a wide range of aldose sugars. This study demonstrates the role of different organic acids in mineral phosphate solubilization by rhizobacteria depending on the nature of the available carbon source.     

The production of ethanol plus fructose sweetener using fructose utilization negative mutants of Zymomonas mobilis

Summary Two mutants, unable to utilize fructose (Fru^–) as a sole source of carbon and energy, were isolated fromZymomonas mobilis following ethyl methane sulfonate (EMS) mutagenesis. The frequency of stable Fru^– mutants among survivors of mutagenesis was 1 in 10⁴. The two Fru^– mutants were able to cleave sucrose to glucose and fructose, and then ferment only the glucose to ethanol while accumulating fructose close to the theoretical value. Under controlled fermentation conditions, sucrose was converted to ethanol plus 80% or higher purity fructose syrup in a single-stage batch fermentation process, improving the Sucrotech Process significantly.     

The Production of Bacillus cereus Enterotoxins Is Influenced by Carbohydrate and Growth Rate

Enterotoxin production is a key factor in Bacillus cereus food poisoning. Herein, the effect of the growth rate (μ) on B. cereus toxin production when grown on sucrose was studied and the Hemolytic BL enterotoxin (HBL) and nonhemolytic enterotoxin (Nhe) production by B. cereus was compared according to carbohydrate at μ = 0.2 h⁻¹. The anaerobic growth was carried out on continuous cultures in synthetic medium supplemented with glucose, fructose, sucrose, or an equimolar mixture of glucose and fructose. Concerning the HBL and Nhe enterotoxin production: (1) the highest enterotoxin production has occurred at μ = 0.2 h⁻¹ when growing on sucrose; (2) HBL production was repressed when glucose was consumed and the presence of fructose (alone or in mixture) cancelled glucose catabolite repression; (3) the consumption of sucrose increased Nhe production, which was not affected by the catabolite repression. Furthermore, analysis of the fermentative metabolism showed that whatever the μ or the carbon source, B. cereus used the mixed acid fermentation to ferment the different carbohydrates. The enterotoxin productions by this strain at μ = 0.2 h⁻¹ are highly influenced by the carbohydrates that do not involve any fermentative metabolism changes.     

Influence of carbon and nitrogen sources on antifungal metabolite production by bacterium associated with entomopathogenic nematode against Penicillium expansum

A specific symbiotic Bacillus sp. isolated from a rhabditid entomopathogenic nematode, Rhabditis (Oscheius) sp. was found to produce large number of bioactive compounds. The present study was conducted to determine the effect of carbon and nitrogen sources for the production of antimicrobial substances by Bacillus sp. The yield of the crude antimicrobial substances and antimicrobial activity against the test micro-organism also differed significantly when carbon and nitrogen sources in the fermentation media were changed. The antifungal activity was significantly high in yeast extract plus fructose (46.5?±?2.12?mm) followed by yeast extract plus maltose, beef extract plus fructose and meat infusion plus glucose. High pressure liquid chromatography analysis of the crude antimicrobial substances revealed different peaks with different retention time indicating that they produced different compounds. When the carbon source was not included in the fermentation media, the antimicrobial production was substantially reduced. The results indicate that carbon source in the fermentation media plays a vital role in the production of antifungal substances. It is concluded that yeast extract and fructose as nitrogen and carbon sources produced maximum activity, which can effectively control the blue mould caused by Penicillium expansum in apples and pears.     

甘油影响红曲菌产色素的碳源选择性探究

红曲菌(Monascus spp.)是我国重要的药食同源微生物,红曲色素(Monascus pigments,MPs)是其主要次级代谢产物之一。有研究表明,甘油可促进红曲菌产MPs,但作用机制不明。以丛毛红曲菌(Monascus pilosus)MS-1为实验菌株,考察甘油与葡萄糖或蔗糖复合对红曲菌产MPs的影响。在不含碳源的合成培养基中,将甘油与葡萄糖或蔗糖复合,采用分光光度法和高效液相色谱法等分析MPs的产量和组分、生物量及发酵液pH。当甘油与葡萄糖复合,添加甘油后发酵液pH、生物量无显著变化(P0.05),总色价显著降低(P0.05)。当2 g/L或40 g/L甘油与蔗糖复合,发酵液pH显著降低而生物量及总色价显著增加(P0.05)。当40 g/L甘油与蔗糖复合时,总色价是仅以蔗糖为碳源时的16.5倍,且MPs同系物数量明显增多(P0.05)。在合成培养基条件下,甘油促进红曲菌产MPs具有碳源种类的选择性。该结果可为研究甘油影响红曲菌产MPs的作用机制提供参考,为甘油用于MPs生产提供依据。     

The kinetics of simultaneous glucose and fructose uptake and product formation by Aspergillus niger in citric acid fermentation

The kinetics of substrate uptake and product formation in the process of citric acid accumulation by Aspergillus niger on sucrose as a sole carbon source are presented. The experiments are aimed at studying if glucose and fructose obtained from the hydrolysis of sucrose are equivalent carbon sources for A. niger and how the presence of the two different carbon substrates might influence the citric acid formation process. Beet sugar was used as a sole carbon source in the first series of experiments conducted in two types of bioreactors: stirred tank and air-lift. The fructose uptake rate was significantly lower than the glucose uptake rate in the late idiophase. A substrate utilisation breakpoint occurred when a large amount of citric acid was accumulated in the fermentation broth. A similar phenomenon was also detected in repeated fed-batch fermentation. This phenomenon was confirmed by the second series of parallel shake culture runs, in which fungal growth and citric acid accumulation by A. niger was simultaneously tested on the media containing the following carbon sources: sucrose, glucose and fructose, with and without addition of concentrated citric acid solution. Finally, it was shown that high concentration of citric acid strongly depleted fructose uptake rate.     

Homofermentative production of optically pure <Emphasis Type="SmallCaps">l</Emphasis>-lactic acid from sucrose and mixed sugars by batch fermentation of <Emphasis Type="Italic">Enterococcus faecalis</Emphasis> RKY1

In the present study, lactic acid fermentation was carried out by batch culture of Enterococcus faecalis RKY1 using sucrose and mixed sugars as the major substrate. Maximum lactic acid productivity (5.2 g/L/h) was recorded when 50 and 100 g/L of sucrose were used as a carbon source. Sucrose concentration higher than 150 g/L resulted in the decrease of lactic acid productivity due to inhibition by high substrate concentration, but lactic acid productivity was remained > 3.0 g/L/h until the sucrose used for lactic acid fermentation increased up to 150 g/L. L-Lactic acid content of the total lactic acid produced from sucrose and mixed sugars was higher than 98%. When the fermentation media contained sucrose, the kinetic parameters showing specific rates such as μ, qS, and qP were relatively lower than those of fermentation using glucose as a sole carbon source, which might be due to additional time requirement to induce invertase enzyme for utilization of sucrose. There was no carbon catabolite repression observed when the sugar mixtures containing sucrose, glucose, and/ or fructose were used as a carbon source for lactic acid fermentation by E. faecalis RKY1.     

Influence of carbon and nitrogen sources on Flavobacteriumgrowth and zeaxanthin biosynthesis

Growth and production of zeaxanthin by Flavobacterium sp were studied using different carbon and nitrogen sources in a chemically defined medium. The best growth was supported by sucrose, but glucose yielded similar carotenoid concentrations. Both asparagine and glutamine stimulated growth and pigment formation. Carotenoid production and glucose consumption increased as a function of asparagine concentration. In the presence of asparagine, high glucose concentrations decreased pigment production without affecting biomass formation. In the absence of glucose, asparagine could not support growth and zeaxanthin production. When compared to the effect of 55 mM glucose, 10 mM oxaloacetate increased growth and carotenoid production. Pyruvate and other intermediates of the citric acid cycle showed a similar stimulatory effect. The intermediates of glycolysis: glucose 6-phosphate and fructose 1,6-diphosphate did not support growth. These results suggest that Flavobacterium sp utilizes asparagine primarily as a nitrogen source for growth and production of zeaxanthin. Received 29 September 1998/ Accepted in revised form 23 April 1999     

Production of extracellular polyols in Aureobasidium pullulans

Aureobasidium pullulans produced extracellularly considerable amounts of polyols in the media with sucrose, glucose, fructose and mannose as sole carbon source during the late exponential and stationary phase of growth. The maximum yield of polyol was about 23% in the 20%(w/v) sucrose medium, of which mannitol was the main polyol associated with minute quantities of glycerol. Stress solutes such as NaCl and KCl did not promote polyol production.     

Antifungal activity of crude extract produced by Bacillus sp. associated with entomopathogenic nematode from media formulated by six nitrogen sources with fructose against Penicillium expansum

A specific symbiotic Bacillus species isolated from a rhabditid entomopathogenic nematode, Rhabditis (Oscheius) sp. was found to produce a number of bioactive compounds. The present study was conducted to determine the effect of six different nitrogen sources in combination with fructose on the production of antifungal crude extract by Bacillus sp. against Penicillium expansum. The yield of crude extract and antifungal activity against the test fungi differed significantly when the nitrogen sources in the fermentation media were changed. The highest yield was recorded for beef extract plus fructose (921?mg/L). The antifungal activity was higher in yeast extract plus fructose [P. expansum (46.5?±?2.12?mm)], followed by beef extract. High performance liquid chromatography analysis of the crude antimicrobial substances revealed different peaks with different retention times indicating that they produced different compounds. When a carbon source was not included in the fermentation medium, the antimicrobial production was substantially reduced almost eight times. Carbon source in the fermentation medium plays a vital role in the production of antimicrobial substances. Yeast extract and fructose as nitrogen and carbon sources in the fermentation medium produced maximum antimicrobial activity.     

Sorbitol production by Zymomonas mobilis

Summary High resolution ¹³C Nuclear Magnetic Resonance (NMR) spectroscopy has been employed to determine the chemical composition of the unknown major products in a sucrose or fructose plus glucose fermentation to ethanol by the bacterium Zymmonas mobilis. When grown on these sugars Z.mobilis was found to produce significant amounts of sorbitol, up to 43 g·l^-1 for strain ZM31 when grown on 250 g·l^-1 sucrose.The production of sorbitol and decrease of glucose, fructose, or sucrose was followed throughout batch fermentations by NMR and HPLC. Sorbitol was shown to be derived only from fructose by [¹⁴C]-feeding experiments. Additionally ³¹P NMR spectroscopy was utilized to determine the concentrations of both glucose 6-phosphate and fructose 6-phosphate relative to their respective concentrations in Z.mobilis cells fermenting glucose or fructose alone.It is suggested that free glucose inside the cell inhibits fructokinase. Free intracellular fructose may then be reduced to sorbitol via a dehydrogenase type enzyme. Attempts to grow Z.mobilis on sorbitol were unsuccessful, as were experiments to induce growth via mutagenesis.This work was supported in part by the National Energy Research, Development and Demonstration Council of Australia     

Influence of selected sugars and temperature on fatty acids composition in Candida lipolytica

Summary An investigation was made of the effects of temperature and of mono- and disaccharides on lipids, biomass, odd-chain and unsaturated fatty acids production of Candida lipolytica. With different sugars as carbon source at 30°C, the order for biomass production was: fructose > glucose > sucrose > lactose > galactose, while lipids production/g biomass decreased as follows: lactose, sucrose, galactose, fructose and glucose. On the other hand, the odd-chain fatty acids contents decreased in the following order: fructose, lactose, glucose, sucrose and galactose. Lowering the temperature of cultivation to 15°C, biomass, lipids and unsaturated fatty acids decreased. However, a notable decrease in the content of odd-chain fatty acids was detected.     

Effects of the carbon source and the interaction between carbon sources on the physiology of the industrial Saccharomyces cerevisiae CAT-1

Abstract

During industrial fermentation, wild isolates are able to persist and even predominate in the bioreactors. Saccharomyces cerevisiae CAT-1 was one of these isolates and now is one of the yeasts mostly used in industrial ethanol processes in Brazil due to its efficient fermentation capacity. Despite it, the strain’s physiology has been marginally studied so far. Since strains of the same species may have different responses to a specific cultivation condition, this work aimed to evaluate the physiology of S. cerevisiae CAT-1 in batch cultures using different carbon sources (glucose, fructose, sucrose, maltose, and galactose) as a sole carbon source and in binary mixtures, at 30 and 37?°C. The results showed that the fructose, sucrose, and maltose were the sugars that presented the highest ethanol yields on the substrate (0.40?g_ethanol g_substrate^?1) at both temperatures. Galactose was the sugar that the yeast had the lowest affinity given the lowest maximum specific growth rate (0.28?h^?1). Despite the influence of a variety of mechanisms for sugar transport, the cells consume first substrates with fewer metabolic steps to catabolism and are susceptible to adaptive evolution depending on the availability of substrate.     

Sugar utilization by yeast during fermentation

Summary When glucose and fructose are fermented separately, the uptake profiles indicate that both sugars are utilized at similar rates. However, when fermentations are conducted in media containing an equal concentration of glucose and fructose, glucose is utilized at approximately twice the rate of fructose. The preferential uptake of glucose also occurred when sucrose, which was first rapidly hydrolyzed into glucose and fructose by the action of the enzyme invertase, was employed as a substrate. Similar results were observed in the fermentation of brewer's wort and wort containing 30% sucrose and 30% glucose as adjuncts. In addition, the high levels of glucose in the wort exerted severe catabolite repression on maltose utilization in theSaccharmyces uvarum (carlsbergensis) brewing strain. Kinetic analysis of glucose and fructose uptake inSaccharomyces cerevisiae revealed aK _m of 1.6 mM for glucose and 20 mM for fructose. Thus, the yeast strain has a higher affinity for glucose than fructose. Growth on glucose or fructose had no repressible effect on the uptake of either sugar. In addition, glucose inhibited fructose uptake by 60% and likewise fructose inhibited, glucose uptake by 40%. These results indicate that glucose and fructose share the same membrane transport components.     

Glucose, and not sucrose, is transported from wheat to wheat powdery mildew

The main host carbon energy source transferred from wheat leaves (Triticum aestivum L.) to wheat powdery mildew (Erysiphe graminis f.sp. tritici) has been investigated in three ways. When the uptake of sugars by isolated mycelial suspensions was examined, the uptake rate for glucose was considerably higher than that for a range of other solutes. Analysis by high-performance liquid chromatography of leaf and mycelial extracts following uptake of sugars into infected leaf pieces confirmed that sucrose was rapidly hydrolyzed in the leaf; no sucrose or fructose could be detected in mycelial extracts. Furthermore, studies of the uptake of asymmetrically labelled sucrose indicated that this sugar is cleaved prior to uptake by the pathogen. Thus several lines of evidence show that glucose, and not sucrose, is the major carbon energy source transferred from host to fungal mycelium. Received: 11 November 1998 / Accepted: 18 January 1999     

Effect of different carbon sources on the production of succinic acid using metabolically engineered Escherichia coli

Succinic acid (SA) is an important platform molecule in the synthesis of a number of commodity and specialty chemicals. In the present work, dual-phase batch fermentations with the E. coli strain AFP184 were performed using a medium suited for large-scale industrial production of SA. The ability of the strain to ferment different sugars was investigated. The sugars studied were sucrose, glucose, fructose, xylose, and equal mixtures of glucose and fructose and glucose and xylose at a total initial sugar concentration of 100 g L-1. AFP184 was able to utilize all sugars and sugar combinations except sucrose for biomass generation and succinate production. For sucrose as a substrate no succinic acid was produced and none of the sucrose was metabolized. The succinic acid yield from glucose (0.83 g succinic acid per gram glucose consumed anaerobically) was higher than the yield from fructose (0.66 g g-1). When using xylose as a carbon source, a yield of 0.50 g g-1 was obtained. In the mixed-sugar fermentations no catabolite repression was detected. Mixtures of glucose and xylose resulted in higher yields (0.60 g g-1) than use of xylose alone. Fermenting glucose mixed with fructose gave a lower yield (0.58 g g-1) than fructose used as the sole carbon source. The reason is an increased pyruvate production. The pyruvate concentration decreased later in the fermentation. Final succinic acid concentrations were in the range of 25-40 g L-1. Acetic and pyruvic acid were the only other products detected and accumulated to concentrations of 2.7-6.7 and 0-2.7 g L-1. Production of succinic acid decreased when organic acid concentrations reached approximately 30 g L-1. This study demonstrates that E. coli strain AFP184 is able to produce succinic acid in a low cost medium from a variety of sugars with only small amounts of byproducts formed.