• Food Science and Biotechnology
• /
• v.15 no.4
• /
• pp.647-649
• /
• 2006

Mevinolin, a fungal metabolite, is a potent inhibitor of 3-hydroxy-methyl-3-glutaryl-coenzyme A (HMG-CoA) reductase, the rate-controlling enzyme in cholesterol biosynthesis. In this investigation, the optimum factors for mevinolin production by Monascus pilosus IFO 480 in soymeal fermentation were studied. The highest yield of mevinolin, 2.82 mg mevinolin per g dry weight, without citrinin (a toxic fungal secondary metabolite) was obtained after 21 days of fermentation at $30^{\circ}C$ at 65% moisture content, particle size 0.6-0.9 mm, and initial substrate pH of 6.0. Mevinolin was present in the fermentation substrate predominantly in the hydroxycarboxylate form (open lactone, 92.1-97.3%), which is currently being used as a hypocholesterolemic agent.

• KSBB Journal
• /
• v.15 no.4
• /
• pp.380-387
• /
• 2000

An extractive fermentation process using pervaporation was studied in a 7 liter fermentor. Pervaporation was performed using a silicone membrane module and a low-acid-producing strain Clostridium acetobutylicu, B18 was used to produce butanol. In batch culture without pervaporation pH 5.5 and initial glucose concentration of 60 g/L resulted in the highest butanol productivity (0.216 g/L$.$h) with butanol yield of 0.261 Butanol flux through the membrane was best at 2.0 L/min-tubing of air flow rate In batch and fed-batch fermentation glucose consumption rate increased by 1.3 times with pervaporation.

• Journal of Microbiology and Biotechnology
• /
• v.21 no.5
• /
• pp.519-524
• /
• 2011

The correlation between alcoholic fermentation rate, measured as carbon dioxide ($CO_2$) evolution, and the rate of hydrogen sulfide ($H_2S$) formation during wine production was investigated. Both rates and the resulting concentration peaks in fermentor headspace $H_2S$ were directly impacted by yeast assimilable nitrogenous compounds in the grape juice. A series of model fermentations was conducted in temperature-controlled and stirred fermentors using a complex model juice with defined concentrations of ammonium ions and/or amino acids. The fermentation rate was measured indirectly by noting the weight loss of the fermentor; $H_2S$ was quantitatively trapped in realtime using a pre-calibrated $H_2S$ detection tube which was inserted into a fermentor gas relief port. Evolution rates for $CO_2$ and $H_2S$ as well as the relative ratios between them were calculated. These fermentations confirmed that total sulfide formation was strongly yeast strain-dependent, and high concentrations of yeast assimilable nitrogen did not necessarily protect against elevated $H_2S$ formation. High initial concentrations of ammonium ions via addition of diammonium phosphate (DAP) caused a higher evolution of $H_2S$ when compared with a non-supplemented but nondeficient juice. It was observed that the excess availability of a certain yeast assimilable amino acid, arginine, could result in a more sustained $CO_2$ production rate throughout the wine fermentation. The contribution of yeast assimilable amino acids from conventional commercial yeast foods to lowering of the $H_2S$ formation was marginal.

• Journal of Microbiology and Biotechnology
• /
• v.23 no.9
• /
• pp.1253-1259
• /
• 2013

The influences of glucose concentration, initial medium acidity (pH), and temperature on the growth and ethanol production of Saccharomyces cerevisiae NK28, which was isolated from kiwi fruit, were examined in shake flask cultures. The optimal glucose concentration, initial medium pH, and temperature for ethanol production were 200 g/l, pH 6.0, and $35^{\circ}C$, respectively. Under this growth condition, S. cerevisiae NK28 produced $98.9{\pm}5.67$ g/l ethanol in 24 h with a volumetric ethanol production rate of $4.12{\pm}0.24g/l{\cdot}h$. S. cerevisiae NK28 was more tolerant to heat and ethanol than laboratory strain S. cerevisiae BY4742, and its tolerance to ethanol and fermentation inhibitors was comparable to that of an ethanologen, S. cerevisiae D5A.

• Microbiology and Biotechnology Letters
• /
• v.19 no.4
• /
• pp.390-397
• /
• 1991

Ethanol production by calcium alginate-immobilized baker's yeast (Saccharor/tyces cereviszae) was studied in the batch fermentation using glucose medium as a feed. Immobilied cells were stable between $30^{\circ}C$ and $40^{\circ}C$ whereas free cells were stable between $30^{\circ}C$ and $37^{\circ}C$ The beads were showed constant ethanol productivity during 720 hours (30 days) over. Fermentation characteristics of immobilized baker's yeast were examined changing the initial glucose concentration of broth in fermentation. Initial glucose concentrations employed were 50, 100, 150 and 200 g/l, respectively. In 15% gucose medium, maximum specific growth rate, maximum ethanol yield and ethanol concentration were observed as 0.092 $h^{-1}$, 0.45, 67.5 g/l, respectively.

• Asian-Australasian Journal of Animal Sciences
• /
• v.18 no.12
• /
• pp.1727-1734
• /
• 2005

The fermentation characteristics and mono- and di-saccharides compositions during the early stage of ensiling were studied with a temperate grass, Italian ryegrass (Lolium multiflorum Lam.) and a tropical grass, guineagrass (Panicum maximum Jacq.). The laboratory silos were kept in the room set at 25$^{\circ}C$, and then were opened on 0.5, 1, 2, 3, 5 and 7 days (14 days in Italian ryegrass) after ensiling, respectively. The Italian ryegrass silage showed a fast and large pH decrease caused by a fast and large production of lactic acid during the first 5 days of ensiling and succeeded to achieve lactic acid type fermentation; high lactic acid/acetic acid and lactic acid content at the end of ensiling (14 days), low values of pH (3.74), acetic acid, ethanol and ammonia-N/total nitrogen, none or only small amounts of Butyric acid, valeric acid and propionic acid. The guineagrass silage showed a slow decrease in pH and a slow increase in lactic acid content during the full ensiling period, causing a high final pH value, low contents of lactic acid, acetic acid, total volatile fatty acids and total organic acids. In Italian ryegrass silage, mono- and di-saccharides compositions decreased largely within the initial 0.5 day (12 h) of ensiling. Sucrose disappeared rapidly within the initial 0.5 day of ensiling, but fructose and glucose contents showed an initial rise by the activity of enzymes in plant tissues, and then decreased gradually. On the other hand, the contents of monoand di-saccharides in guineagrass showed the largest decreases due mainly to plant respiration within the initial 0.5 day of ensiling, and no initial rises in fructose and glucose contents during the early stage of ensiling because of the absence of fructans which are hydrolyzed into fructose and glucose in temperate grasses. In both silages, the rate of reduction in mono- and di-saccharides compositions within the initial 5 days of ensiling was ranked in the order of glucose>fructose>sucrose, suggesting that glucose and fructose might be more favorably utilized than sucrose by microorganisms and glucose is the first fermentation substrate. It was concluded that the silage made from Italian ryegrass with high moisture content had a good fermentation quality owing to the dominance of lactic acid bacteria and active lactic acid fermentation during the initial stage of ensiling. These results can be explained by rapid plant sap liberation and the high activity of plant enzyme hydrolyzed fructans into fructose and glucose within the initial 2 days of ensiling, which stimulate the homofermentative lactic acid bacteria growth. In ensiling a temperate grass, the physical characteristics may ensure the rapid onset of fermentation phase, which results from the smaller losses of water-soluble carbohydrates during the initial stage of ensiling and providing sufficient water-soluble carbohydrates for lactic acid bacteria. The silage made from guineagrass with intermediate dry matter and high initial mono- and di-saccharides content was stable silage. This could be explained by the higher incorporation of air during the very early stage of ensiling and the restriction of cell breakdown and juice release due to the properties of a tropical grass with coarse porosity and stemmy structures. These physical characteristics delayed the onset of lactic acid bacteria fermentation phase by extending the phases of respiration and aerobic microorganisms activity, causing the higher loss of water-soluble carbohydrates and the shortage of lactic acid bacteria fermentation substrates.

• Asian-Australasian Journal of Animal Sciences
• /
• v.18 no.9
• /
• pp.1273-1278
• /
• 2005

This study is to evaluate the effect of different levels of ensiling density on the fermentation quality of guineagrass silages during the early stage of ensiling. Guineagrass at the milky ripe stage was chopped and ensiled into a small-scale laboratory silo at two ensiling density levels (high density at 95 g/silo and low density at 75 g/silo). Three silos per level were opened after six ensiling periods (0.5, 1, 1.5, 2, 3 and 7 days of ensiling) and the fermentation qualities were analyzed. Within the initial 1.5 days of ensiling there were not significant (p>0.05) differences in the fermentation qualities between two density levels silages, and an almost constant pH and no or only small amounts of lactic acid, acetic acid and total volatile fatty acids were detected. However, the high density silage significantly (p<0.05) increased the rate and extent of fermentation after 1.5 days of ensiling, which was well reflected in significantly (p<0.05) faster and larger pH decline and lactic acid production at each elapsed time as compared with the low density silage. This resulted in significantly (p<0.05) lower finial pH and significantly (p<0.05) higher lactic acid content at the end of the experiment. Moreover, there was higher AA content relative to LA in both the H-D and L-D silages during the full fermentation course, and resulted in the AA-type silage. There were generally somewhat or significantly (p<0.05) higher acetic acid, volatile fatty acids and ammonia-N/total nitrogen in the high density silage than in the low density silage during the initial 3 days of ensiling. However, there were higher (p>0.05) ammonia-N/total nitrogen and significantly (p<0.05) higher butyric acid content in the low density silage at day 7 of ensiling. The silages of two density levels showed an initial increase in glucose between 0.5 and 1 day for the high density silage and between 1 and 1.5 days for the low density silage, respectively, thereafter showed a large decrease until the end of the experiment. There were not large differences (p>0.05) in ethanol content between the low density and high density silages that showed small amounts within initial 3 days of ensiling. However, the low density silage had a significantly (p<0.05) higher ethanol content than the high density silage at the end of experiment. From the above results it was suggested that the increase in ensiling density was an effective method to improve the fermentation quality, especially for tropical grasses.

• Microbiology and Biotechnology Letters
• /
• v.19 no.4
• /
• pp.398-404
• /
• 1991

- Ethanol production by calcium alginate-immobilized baker's yeast was studied in the continuous shaked-flask reactor (CSFR) using glucose medium as a feed. Immobilized cells were stable at 30~$37^{\circ}C$ and pH 4~8. Fermentation characteristics of immobilized baker's yeast were examined changing the initial glucose concentration employed were 50, 100 and 150 g/l, respectively. It was investigated that the influent glucose concentration and the dilution rate have an influence on the ethanol fermentation characteristics at steady state in continuous culture of immobilized baker's yeast. The optimum conditions for high ethanol productivity and low residual glucose output in ethanol prodution were shown to be 0.2 h ' for the dilution rate and 150 g/l for the influent glucose concentration. The maximum ethanol productivity, ethanol yield, specific growth rate and glucose conversion rate were around 7.12 g/$l\cdot h$, 0.23, 0.366 g/$l\cdot h$ and 78.43, respectively.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.55 no.3
• /
• pp.267-277
• /
• 2022

This study investigated changes in the physicochemical and microbiological properties of fermented fish sauces based on the pacific sand lance Ammodytes personatus during fermentation according to rice koji treatments and salt contents. In total, six fish sauces were prepared, with rice koji treatment for 24 or 72 h before salt addition, and salt contents of 10 or 20%, including two controls to compare the response to different salt contents without koji treatment. The initial pH values of the sauces with koji treatments were notably lower than those of the controls. Over the 10 months of fermentation, the amino nitrogen contents of the sauces with 10% salt were higher than those with 20% salt, while the volatile base nitrogen value was also increased. In the microbial community, the initial numbers of lactic acid bacteria and mold were higher in the sauces with koji treatment than in the controls. After 8 months of fermentation, the free amino acid and organic acid contents were higher in the sauces with koji treatment than in the controls. Although the fermentation rate was affected to a greater extent by salt contents, the rice koji treatment also exerted a positive effect on the acceleration of fermentation.

• Journal of Microbiology and Biotechnology
• /
• v.14 no.6
• /
• pp.1163-1169
• /
• 2004

An unstructured mathematical model is presented for lactic acid fermentation based on the energy balance. The proposed model reflects the energy metabolic state and then predicts the cell growth, lactic acid production, and glucose consumption rates by relating the above rates with the energy metabolic rate. Fermentation experiments were conducted under various initial lactic acid concentrations of 0, 30, 50, 70, and 90 g/l. Also, a genetic algorithm was used for further optimization of the model parameters and included the operations of coding, initialization, hybridization, mutation, decoding, fitness calculation, selection, and reproduction exerted on individuals (or chromosomes) in a population. The simulation results showed a good fit between the model prediction and the experimental data. The genetic algorithm proved to be useful for model parameter optimization, suggesting wider applications in the field of biological engineering.