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PubMed2006

Short communication: Effects of Lactobacillus helveticus-fermented milk on the differentiation of cultured normal human epidermal keratinocytes.

Effects of Lactobacillus helveticus-fermented milk whey on the differentiation of normal human epidermal keratinocytes were studied. Analysis using real-time reverse transcription-polymerase chain reaction revealed that addition of Lactobacillus helveticus-fermented milk whey to the culture medium enhanced mRNA expression of keratin 10, an early differentiation marker, as well as involucrin, a late differentiation marker. Whey of artificially acidified milk, prepared by the addition of dl-lactic acid to milk instead of fermentation, also promoted expression of both markers, but Lactobacillus helveticus-fermented milk whey was more effective in increasing expression of those markers. These results indicate that milk whey has the potential to induce multiple stages of keratinocyte differentiation and that fermentation with Lactobacillus helveticus increases that activity. Furthermore, we examined the expression of profilaggrin, which increases with epidermal terminal differentiation, and found that Lactobacillus helveticus-fermented milk whey enhanced expression of profilaggrin mRNA in a dose-dependent manner. Expression also occurred to a greater extent than with artificially acidified milk whey or other whey samples prepared with several lactic acid bacterial species. Because the proteolytically processed form of profilaggrin, filaggrin, is very important for normal epidermal hydration and flexibility, our results indicate that Lactobacillus helveticus-fermented milk whey has the potential to enhance the production of filaggrin-related natural moisturizing factor, because of its effect on the induction of epidermal differentiation, and is expected to be a useful skin moisturizing agent.

Animals↗
PubMed2006

Effect of essential oil active compounds on rumen microbial fermentation and nutrient flow in in vitro systems.

Two experiments were conducted to determine the effects of several essential oil active compounds on rumen microbial fermentation. In the first experiment, 4 doses (5, 50, 500, and 5,000 mg/L) of 5 essential oil compounds were evaluated using in vitro 24-h batch culture of rumen fluid with a 60:40 forage:concentrate diet (18% crude protein; 30% neutral detergent fiber). Treatments were control (CON), eugenol (EUG), guaiacol, limonene, thymol (THY), and vanillin. After 24 h, the pH was determined, and samples were collected to analyze ammonia N and volatile fatty acids (VFA). The highest dose of all compounds decreased total VFA concentration and increased the final pH. Eugenol at 5 mg/L tended to reduce the proportion of acetate and the acetate to propionate ratio, at 50 and 500 mg/L tended to reduce ammonia N concentration, and at 500 mg/L reduced the proportion of propionate and branched-chain VFA concentration, without affecting total VFA concentration. All other treatments had minor effects or changes occurred only after total VFA concentration decreased. In the second experiment, 8 dual-flow continuous culture fermenters (1,320 mL) were used in 3 replicated periods (6 d of adaptation and 3 d of sampling) to study the effects of THY and EUG on rumen microbial fermentation. Fermenters were fed 95 g/d of DM of a 60:40 forage:concentrate diet (18% crude protein; 30% neutral detergent fiber). Treatments were CON, 10 mg/L of monensin (positive control), and 5, 50, or 500 mg/L of THY and EUG, and were randomly assigned to fermenters within periods. During the last 3 d of each period, samples were taken at 0, 2, 4, and 6 h after the morning feeding and analyzed for peptides, amino acids, and ammonia N concentrations, and total and individual VFA concentrations. Monensin changed the VFA profile as expected, but inhibited nutrient digestion. Eugenol and THY decreased total VFA concentration and changed the VFA profile, and only 5 mg/L of THY tended to reduce the proportion of acetate, increased the proportion of butyrate, and increased the large peptides N concentration without decreasing total VFA concentration. Most of these essential oil compounds demonstrated their antimicrobial activity by decreasing total VFA concentration at high doses. However, EUG in batch fermentation and 5 mg/L of THY in continuous culture modified the VFA profile without decreasing total VFA concentration, and EUG in batch fermentation decreased ammonia N concentration.

Acetates↗
PubMed1976

Effects of fermentation time on in vivo/in vitro relationships.

The effects of six fermentation times, 24 through 84 h at 12 h intervals, were studied on in vivo/in vitro relationships and repeatability and variability of in vitro technique. Three stages of maturity each of bermudagrass, bahiagrass, rye-grass, sorghum-sudan, alfalfa, and orchardgrass were used. For one fermentation time for all types of forages, a 48-h fermentation demonstrated the smallest variation among runs and the least run X forage interaction. However, the optimum fermentation for perennials as a group was 60 h; and for annuals, legumes, and temperate grasses it was 36 h. Further studies in vitro compared a 48-h fermentation for all types of forage with 36 h for annuals and 60 h for perennials. Forty-eight forages, including 20 annuals and 28 perennials, were digested in vitro during three runs. With the 48-h fermentation, forages accounted for 86.43% of the total variation, runs 6.80%, and run X forage interaction 6.44%. Variation due to runs was reduced to .33%, and run X forage interaction to .90%, for a combined 36- and 60-h fermentation for annuals and perennials, respectively. Variation due to forage was increased to 98.53%.

Animal Feed↗
PubMed1980

Performance of calves fed fermented mastitic milk, colostrum, and fresh whole milk.

Weight gains, milk intake, and health of calves fed fermented mastitic milk from cows treated and not treated with antibiotics were compared with those of calves fed fermented colostrum or fresh normal milk at two intakes. Calves fed fermented mastitic milk from cows treated with antibiotics, not treated with antibiotics, fermented colostrum (diluted 1:1 with water), and fresh normal milk gained .13, .14, .13, and .10 kg/day in trial 1 fed at 8% of body weight daily, and .09, .11, .18, and .13 dg/day in trial 2 fed at 10% of body weight daily from birth through 30 days of age. All calves were housed in individual pens during milk feeding. Feeding milk at 10% in trial 2 did not improve gains over those in trial 1. Incidence of health disorders and mastitis in first lactation of cows fed fermented mastitic milk as calves was not different from those of cows fed fresh normal milk or fermented colostrum. Fermented mastitic milk appears to be an economical and safe feed for rearing calves when calves are housed individually during milk feeding.

Animals↗
PubMed1992

Influence of rumen fermentable neutral detergent fiber levels on feed intake and milk production of dairy cows.

Sixteen dairy cows in midlactation were fed four isonitrogenous (mean 2.46% N) mixed rations containing 46.4% DM and 40.7% NDF in a 16-wk Latin square design experiment. Diets were 42% barley-based concentrate, on a DM basis; forage was provided by combinations of two timothy silages of either slow (poor timothy) or rapid (good timothy) rumen fermentability and an alfalfa silage. Differences between the timothy forages caused the 24-h in sacco mixed diet NDF fermentability, determined in dry cows fed hay, to be 53.8, 56.0, 60.2, and 62.1% in the four diets formulated to rise from 0% [as a percentage of total timothy DM] to 33, 66, and 100% good timothy. Intake of DM and NDF were not influenced by forage source. Rumen pool sizes of OM and NDF were similarly unaffected by treatment. Milk production increased linearly as the proportion of rapidly fermentable NDF in the diet increased, although the increases were small and not statistically significant, whereas BW gain declined (nonsignificantly). As a result, total net energy output was not influenced by diet. Although cows appeared able to extract more energy than expected from the slower fermenting forage, increasing levels in the diet resulted in a shift in energy output from milk products to BW gain, supported by a shift in rumen fermentation end products from propionic to acetic acid. Results do not appear to support the concept that NDF quality influences and can be used to predict voluntary feed intake. There is no indication that cows responded to more rapidly fermentable dietary NDF by increasing feed intake or extent of NDF fermentation in the rumen.

Ammonia↗
PubMed2001

Lactobacillus casei strain Shirota-fermented milk stimulates indigenous Lactobacilli in the pig intestine.

The aim of this study was to determine the effect of a probiotic, i.e. fermented milk prepared with Lactobacillus casei strain Shirota, on indigenous Lactobacilli in the pig large intestine. This fermented milk was given as a probiotic to experimental pigs for 2 weeks. The fecal organic acid concentration increased with the fermented milk; acetate and propionate increased significantly (p<0.05). At the same time, lactate and butyrate tended to increase. The fecal pH was significantly reduced by the fermented milk (p<0.05). Although the number of bacteria of strain Shirota in the intestinal contents was much smaller than those of indigenous Lactobacilli, 10(4) vs 10(8) (cfu/g), the numbers of indigenous Lactobacilli and Bifidobacteria in the pig intestine appeared to increase with the fermented milk. In addition, the phenotypic diversity (phenotypic group numbers) of indigenous Lactobacilli increased from 3 to 8 with the fermented milk supplementation. Thus the fermented milk affected the indigenous Lactobacillus population and constitution.

Animals↗
PubMed2003

[Production of tyramine in "moromi" mash during soy sauce fermentation].

The concentrations of 7 non-volatile amines, tyramine (Tym), histamine (Him), phenethylamine (Phm), putrescine (Put), cadaverine (Cad), spermidine (Spd) and spermine (Spm) in the liquid part of "moromi" mash during soy sauce fermentation were studied. These amines, except for him and Cad, were detected during fermentation by the conventional production method in the laboratory. Put and Spd were detected at the beginning, and Tym, Phm and Spm appeared later; these 5 amines increased gradually during the fermentation. Put, Spd, Spm and Cad were present in the raw starting material for soy sauce; thus, Tym and Phm were produced by the fermentation. When "moromi" mash was added to liquid medium and cultivated, Tym was detected in some "moromi" mash and the other amines were not detected. Tym-producing bacterial strains were isolated from the liquid culture media of Tym-positive "moromi" mash. The Tym-producing strain was a gram-positive coccus. The conditions for production of amines by Tym-producing bacterial strains were examined. These strains grew and produced tyramine under various conditions, which may occur during soy sauce fermentation. Namely, Tym was produced at pH 5-10, at salt concentrations of less than 8%, under either aerobic or anaerobic conditions. During soy sauce fermentation, it is assumed that Tym would be produced by these strains during the early stages of soy sauce aging within a short period when the salt concentration and pH conditions are optimal for growth. Based on the bacteriological properties, the strains were identified as Enterococcus faecium. With the exception of Phm and Him, which did not exist in the starting raw material, non-volatile amines (including Put, Cad, Spd and Spm) were not produced and microorganisms producing them are not believed to be present during "moromi" fermentation.

Bacteria↗
PubMed1992

Lactic acid fermentation of broiler processing waste: physical properties and chemical analyses.

Broiler processing waste (offal), consisting of broiler heads, viscera, and feet, was collected from a commercial processing plant, ground, mixed with a fermentable substrate, and inoculated with actively growing organisms from a commercial silage culture. The offal mixture was fermented at 11, 19, and 37 C for up to 48 h and evaluated for pH, odor, and aqueous, solid, and oil fractions produced by centrifugation. Freshly ground offal, fermented offal, and aqueous and solids fractions were analyzed for moisture, fat, and protein content. The oil fraction produced by centrifugation of the fermented offal was analyzed for fatty acid composition. The optimum fermentation conditions, as determined by final pH, were obtained by the addition of 6% sucrose, inoculation with 10(6) cfu of silage culture organisms/kg of offal, and incubation at 37 C. The pH decreased from 6.2 to 3.9 in 24 h. Freshly ground offal and 48-h fermented offal were found to contain 63.2% moisture, 15.9% fat, and 14.9% protein, and 57.3% moisture, 19.1% fat, and 12.9% protein, respectively. The aqueous and solid fractions were 73.3% moisture, 1.1% fat, and 12.1% protein, and 57.7% moisture, 6.8% fat, and 21.8% protein, respectively. Fermentation was effective in decreasing pH, altering the odor and viscosity, and, upon centrifugation, increasing fat recovery and producing fractions that were easily separated.

Animals↗
PubMed1993

Effect of lactic acid fermentation on bacterial pathogens and indicator organisms in broiler processing waste.

Broiler processing offal (heads, viscera, and feet) was collected on 3 separate days from a commercial processing plant. Each sample was separately ground, supplemented with sucrose (6% initial concentration), inoculated with actively growing lactic acid bacteria (10(6) cfu/g of offal) from a commercial silage culture, and fermented at 37 C. Replicate samples were taken for standard microbiological analysis after 0, 48, and 120 h of fermentation. In fresh offal, heterotrophic plate count, total and fecal coliforms, fecal streptococci, and Aeromonas hydrophila concentrations were 7.4, 5.9, 5.9, 5.4, and 3.9 log10 cfu/g wet weight, respectively. After 48 h of fermentation, the bacterial concentrations were 7.6, 2.2, < 1.3, 5.5, and < 2.3 log10 cfu/g wet weight, respectively. After 120 h of fermentation, the bacterial concentrations were 6.9, < 1.1, < 1.1, < 1.1, and < 1.1 log10 cfu/g wet weight, respectively. Salmonella concentrations in fresh, 48-h fermented, and 120-h fermented offal samples were 3.7, < 1.5, and < 1.5 log10 most-probable-number/100 g wet weight, respectively. Lactic acid fermentation appears to be effective in reducing the number of bacterial pathogens and indicator organisms in poultry processing offal.

Animal Feed↗
PubMed2000

Effects of gamma radiation on sensory qualities, microbiological and chemical properties of salted and fermented squid.

The effects of gamma radiation on sensory quality, microbial population, and chemical properties of salted and fermented squid were investigated. Squid (Todarodes pacificus) was sliced, washed, and then salted with 5, 10, and 20% (wt/wt) sodium chloride. Salted squid was irradiated with dosages of 0, 2.5, 5.0, and 10 kGy of gamma radiation and fermented at 15 degrees C for 50 days. Proximate composition, salinity, water activity, sensory evaluation, and total microbiological populations were examined. Chemical analyses providing information on degree of fermentation, such as amino nitrogen (AN), volatile basic nitrogen (VBN), trimethylamine (TMA), and hypoxanthine (Hx) were also conducted. Irradiated squid was not different in proximate composition, salinity, and water activity from nonirradiated squid. Sensory evaluation scores, total bacteria populations, and pH values were variable depending on salt concentration and irradiation dose. During fermentation, AN, VBN, TMA, and Hx contents increased rapidly as the salt concentration and irradiation dose decreased. Specifically, these chemical compounds of salted and fermented squid prepared with 10% salt and 10 kGy of gamma radiation maintained the appropriate level of fermentation. The present results showed that the combination of low salt concentration (10%) and gamma radiation was effective in processing salted and fermented squid and extending its shelf life compared to control (20% of salt) without adding any food additives.

Animals↗
PubMed2000

[Effect of dissolved oxygen on mutanolysin fermentation].

Effects of several parameters relating to dissolved oxygen(DO) on mutanolysin fermentation were studied. The experiment using shake flasks shows that the medium volume and shaker agitation speed affect the production of mutanolysin. At the same time, the agitation rate together with aeation rate has effects on DO in fermentor. Mutanolysin fermentation was affected by DO greatly. Oxygen is a key restricted factor in mutanolysin fermentation. It affects the metablism and physiological action of Streptomyces globisporus S186. Whatever the DO is excessive high or low, it won't benefit the mutanolysin production. If DO is super, S. globisporus S186 will grow luxuriantly but do not produce mutanolysin, while if DO is lower, the S. globisporus S186 won't grow well even not to produce mutanolysin. During the course of fermentation, the DO changed regularly. It is similar to many antibiotic fermentation and some amino acid fermentation. As S. globisporus S186 grow in exponential phase, DO begin to decrease rapidly from 6 h and get to the lowest point at 40 h or so. Subsequently mutanolysin starts to be produced. DO rises again from 90 h. The key technoloyg of oxygen control in the fermentation is to keep the DO at a suboptimum level. In order to get a high mutanolysin yield, during the culture in fermentor the agitation rate and aeration rate should be kept at 200 r/min and 1:0.8(V:V) respectively.

Endopeptidases↗
PubMed2001

Analysis of single-chain antibody production in Pichia pastoris using on-line methanol control in fed-batch and mixed-feed fermentations.

In the last few years the Pichia pastoris expression system has been gaining more and more interest for the expression of recombinant proteins. Many groups have employed fermentation technology in their investigations because the system is fairly easy to scale up and suitable for the production in the milligram to gram range. A large number of heterologous proteins from different sources has been expressed, but the fermentation process technology has been investigated to a lesser extent. A large number of fermentations are carried out in standard bioreactors that may be insufficiently equipped to meet the demands of high-cell-density fermentations of methylotrophic yeasts. In particular, the lack of on-line methanol analysis leads to fermentation protocols that may impair the optimal expression of the desired products. We have used a commercially available methanol sensor to investigate in detail the effects of supplementary glycerol feeding while maintaining a constant methanol concentration during the induction of a Mut(+) strain of Pichia pastoris. Specific glycerol feed rates in the range of 38-4.2 mg. g(-1). h(-1) (mg glycerol per gram fresh weight per hour) were investigated. Expression of the recombinant scFv antibody fragment was only observed at specific feed rates below 6 mg. g(-1). h(-1). At low specific feed rates, growth was even lower than with methanol as the sole carbon source and the harvest expression level of the scFv was only half of that found in the control fermentation. These results show that glycerol inhibits expression driven by the AOX1 promoter even at extremely limited availability and demonstrate the benefits of on-line methanol control in Pichia fermentation research.

Bioreactors↗
PubMed2001

Impact of cold and dilute sewage on pre-fermentation--a case study.

The municipal sewage treatment plant (STP) of the city of Ghent (Belgium) has to be retrofitted to a 43%-increase in the nitrogen treatment capacity and to phosphorus removal. Cold weather, dilute sewage and a critical COD over N ratio make the retrofit a challenge for full biological nutrient removal. The potential for fermentation of primary sludge to alter those critical feed sewage characteristics was experimentally evaluated. The idea was that the pinpoint introduction of fermentate could optimise the available reactors by achieving high-rate denitrification and enhanced biological phosphorus removal. The fermentation process was evaluated with a bench scale apparatus. At 20 degrees C (heated process), the hydrolysis yield--expressed in terms of soluble COD--varied from 11% to 24% of the total sludge COD. The fermentation yield expressed in VFA COD varied from 8% to 13% of the total sludge COD. The efficiency of heated fermentation of primary sludge was lower during cold and wet weather, due to the different sewage characteristics, as a result of extended dilution periods and low temperature. The raw sewage, the primary effluent and the fermentate were fractionated according to the requirements for the IAWQ Activated Sludge Model No. 2d. The results clearly show that fermentation in the sewer played an important role and temperature was the driving parameter for the characteristics of the dissolved COD. Instead, the weather flow conditions were the driving parameter for the characteristics of the suspended COD. The results of the detailed fractionation were used as background for process evaluation. The final scenario choice for the retrofit depends on a cost-efficiency calculation.

Belgium↗
PubMedDate not supplied

Prevention by long-term fermented miso of induction of colonic aberrant crypt foci by azoxymethane in F344 rats.

The present study was designed to investigate the effects of fermented miso in the diet on the induction of aberrant crypt foci (ACF) by azoxymethane (AOM) in male F344 rats. A total of 50 rats, 8 weeks of age, were divided into 5 groups and given weekly subcutaneous injections of AOM (15 mg/kg body wt) for 3 weeks. Rats were fed a normal control MF solid diet, or solid diet containing 10% long-term fermented (aged), medium- or short-term fermented miso, or 2.2% NaCl for 5 weeks, starting one week before the first AOM dosing. It was found that, compared to the control (MF) diet, the long-term fermented diet significantly decreased (by 22.2%) ACF/colon, but increased (by 18.2%) the number of aberrant crypts (Acs)/focus. The latter was also increased by the medium-term fermented diet (by 25.3%). The PCNA labeling index was only affected by the short-term fermented diet (36.9% increase) and by 2.2% NaCl diet (27.2% increased). The present results indicate that aged or completely fermented miso supplemented into the diet, could act as a chemopreventive agent for colon carcinogenesis.

Animals↗
PubMed2002

Effects of volatile fatty acids on a thermophilic anaerobic hydrogen fermentation process degrading peptone.

Hydrogen fermentation using glucose as a single substrate caused abrupt pH drops and the gradual losses of hydrogen producers, which in turn led to system failure. In this study the use of a proteinaceous substrate, peptone, avoided the abrupt pH drops in the reactive system and allowed for further exploration of volatile fatty acids (VFAs) and pH effects on the hydrogen fermentation process. Our results showed that: (1) during the hydrogen fermentation tests, the abrupt pH drops were avoided thus system stability increased due to the production of ammonia from the peptone fermented, (2) pH control was not necessary and the addition of acetate to the process had little effect on the hydrogen fermentation process, (3) at the extreme pHs the addition of acetate either lengthened the lag phase (pH < or = 6) or slowed the hydrogen production rate (pH > or = 8), and both situations were not desired, and (4) high VFA content in the system sped up the consumption of hydrogen gas. Results of this study suggested that the hydrogen fermentation using the protein-containing substances as substrate was beneficial in maintaining the system pH. As long as the pH was maintained around 6-8, system inhibition due to VFAs accumulation was minimized. Thus, the optimal operation of a hydrogen fermentation process would be achievable via the control of substrate composition at a certain carbohydrate-to-protein ratio.

Bioelectric Energy Sources↗
PubMed1992

[In vitro simulation of rabbit cecal fermentation in a semi- continuous flow fermentor. I. Role of food substrate pretreatment].

A Rusitec semi-continuous flow fermentor was used to study the influence of enzyme pretreatment of food substrates on the fermentation profile over a 2-week period following inoculation with rabbit caecal contents. Three types of substrate were examined: 1) homogenized commercial rabbit feed; 2) the solid remains of this feed after digestion with alpha-amylase for 24 h; and 3) substrate 2 digested for 4 h with pepsin (double enzyme treatment). One of a pair of nylon pouches containing 15 g substrate was replaced each day, thus producing a uniform 48-h fermentation. Fermentation of the untreated feed (1) for 5-6 days produced a fermentation profile quite different from that obtained in vivo in the rabbit caecum: propionic acid accounted for over 35% of total volatile fatty acid (VFA), and butyric acid for about 15%. Amylase digestion (2) gave a stable ferment profile closer to the in vivo profile, except that propionic and butyric acids were similar at 15% of total VFA. Digestion with both amylase and pepsin (3) produced a stable fermentation profile very close to the in vivo profile: C2 > 60%, C3 < 11% and 17% < C4 < 21%. The rate at which membrane constituents (acid detergent fibre, ADF) were lost in 48 h was similar to the digestibility coefficient measured in vivo by others for the same basic feed. Lastly, there was a high percentage (about 5%) of volatile C5 fatty acids; this could be due to the discontinuous fermentor input of one pouch per 24 h. Thus, feed pretreated with both amylase and pepsin simulates, in vitro, rabbit caecal fermentation in a semi-continuous Rusitec type fermentor.

Animal Feed↗
PubMed2004

Effects of substrate components on hydrogen fermentation of multiple substrates.

As is well known, carbohydrate is the most appropriate organic material for hydrogen fermentation, and its hydrogen yield is significantly larger than that of protein. The fermentation of protein began with hydrogen production followed by hydrogen consumption, which helps overall hydrogen recovery. Both carbohydrate and protein are basic components of organic material, and yet carbohydrate is known to be a better substrate than protein in terms of hydrogen yield during hydrogen fermentation. This study used multiple substrates containing different ratios of glucose and peptone as multiple substrates to investigate the roles played by carbohydrate and protein in hydrogen fermentation. The experimental results demonstrated that suitable ratios of glucose and peptone improved the growth of hydrogen producing bacteria. Additionally, a maximum hydrogen yield of 6.4 mmole-H2/g-COD was obtained from the multiple substrate containing 40% peptone and 60% glucose. Most of the produced hydrogen came from fermentation of glucose, not peptone. During hydrogen fermentation, the pH dropped by 1.0 and 1.9 units in 80% and 20% of peptone content in the substrate. Ammonia produced due to peptone degradation neutralized the acids produced from hydrogen fermentation.

Ammonia↗
PubMed2005

[Continuous ethanol fermentation using self-flocculating yeast strain and bioreactor system composed of multi-stage tanks in series].

A continuous ethanol fermentation system composed of four-stage tank fermentors in series and with a total working volume of 4000 mL was established. The first fermentor was designated as the seed fermentor and the others for ethanol fermentation. A self-flocculating yeast strain developed by protoplast fusion of Saccharomyces cerevisiae and Schizosaccharomyces pombe was applied. Two-stage corn powder enzymatic hydrolyzate containing reducing sugar 100 g/L, together with 2.0 g/L (NH4)2HPO4 and KH2PO4, was used as yeast seed culture medium and fed into the seed fermentor at the dilution rate of 0.017h (-1). Meanwhile, the hydrolyzate containing reducing sugar 220 g/L, added with 1.5 g/L (NH4)2HPO4 and 2.5 g/L KH2PO4, was used as ethanol fermentation substrate and fed into the second fermentor at the dilution rates of 0.017, 0.025, 0.033, 0.040 and 0.050 h(-1) (based on the total working volume of the three fermentors), respectively. The chemostat states on which all of the monitoring parameters, including residual sugar, ethanol and yeast cell biomass concentrations, were maintained relatively constant were observed for seed cultivation and ethanol fermentations when the fermentation system was operated at the dilution rates of 0.017, 0.025, 0.033 and 0.050 h(-1). Yeast cells were observed being partly immobilized because significant yeast cell biomass concentration differences between the broth out of and inside the fermentors were detected. Moreover, the oscillations of residual sugar, ethanol and yeast cell biomass concentrations were observed when the fermentation system was operated at the dilution rate of 0.040 h(-1). The broth containing more than 12% (V/V) ethanol and less than 0.11% (W/V) residual reducing sugar and 0.35% (W/V) residual total sugar was produced when the dilution rate was controlled at no more than 0.033 h(-1). The ethanol productivity was calculated to be 3.32(g x L(-1) x h(-1)) for the dilution rate of 0.033 h(-1), which increased nearly 100% compared with that for conventional ethanol fermentation technologies using freely suspended yeast cells.

Bioreactors↗