Rapid Fermentation Research Articles

Distillers draff and forage rape as supplements for store lambs grazing swedes in situ

Cereals are traditionally used as a supplement for store lambs grazing swedes in situ. However Dingwall, Vipond, Brown and Hunter (1989) demonstrated superior lamb growth and slaughter characteristics when soya was used as an alternative supplement to barley. It is thought that under the unusual conditions of high rumen turnover rate and rapid fermentation associated with root feeding a rumen degradable protein to metabolizable energy ratio (RDP:ME) of 10 to 12:1 may be more appropriate than the 7.8:1 normally found in ruminant diets.There may be practical problems associated with feeding soya to lambs outdoors and specialized soya based pellets have been developed. Both soya and soya pellets are relatively expensive and farmers may seek to enhance store lamb growth using cheaper alternative protein sources. The objective of the study reported here was to evaluate distillers draff and forage rape as supplements for store lambs grazing swedes in situ.

Postprandial Changes of Selected Blood and Ruminal Metabolites in Ruminating Calves Fed Diets with or Without Hay

Eight ruminally cannulated Holstein bull calves were used in a switchback design to evaluate effects of hay on post-prandial changes in ruminal pH, ammonia and VFA, blood ketones, and plasma glucose, NEFA, VFA, and urea N. Calves were fed 4.5 kg/d of calf starter with or without hay for ad libitum consumption. Blood and ruminal fluid were sampled every 2h for 12h on d 21 (periods 1 and 2) or d 13 (period 3). Ruminal pH declined from 6.6 at 0h to 5.3 by 2h. Changes in ruminal and plasma VFA were consistent with low pH and rapid fermentation of soluble carbohydrate. Ruminal ammonia, molar percentage butyrate, and blood ketones, plasma urea N, and plasma molar percentage butyrate were lower when hay was fed. Postprandial increases in blood β-hydroxybutyrate and acetoacetate were reduced when hay was fed, and correlated .65 and .50, respectively, to ruminal butyrate. Concentration of β-hydroxybutyrate averaged 1.24 and 1.87 mmol/L at 4h postfeeding. These data suggest that rapid consumption of limited amounts of grain increased in ruminal VFA and blood ketones; increase in ketones was smaller when hay was included in the diet.

High concentration ethanol production using immobilized yeast cells

Rapid fermentation of high concentration glucose solutions (0.555–2.78 kmol/m 3) was achieved in 12–30 h in a batch reactor by optimizing the volume of cell immobilized gel beads in the reactor. At a 0.66:1 volume ratio of gel beads to medium, 2.78 kmol/m 3 glucose was completely fermented in 30 h producing 5.43 kmol/m 3 ethanol with a volumetric productivity of 0.176 kmol/m 3/h. Repeated use of immobilized cells at a glucose concentration of 1.67 kmol/m 3 level for 7 batches produced ethanol consistently in the range of 1.96–2.83 kmol/m3 but did not affect the viability of the cells.

Effect of method of administration of psyllium on glycemic response and carbohydrate digestibility.

To determine whether there was any advantage to taking a soluble fiber supplement separate from food, as opposed to incorporated into a food, we used psyllium as a model, either taken in water just before a flaked bran cereal test meal, sprinkled on top of the cereal, or actually incorporated into the flake. In normal subjects, psyllium reduced the glycemic response when sprinkled onto or incorporated into the cereal, but not when taken before the cereal. Varying the amount of psyllium incorporated into the cereal from 0 to 20% resulted in a linear dose-dependent reduction of the glycemic index (GI) (GI = 101 -2.2 x % psyllium; r = 0.950; p less than 0.002). In subjects with diabetes, the blood-glucose-lowering effect of the psyllium flake cereal was similar to that in normal subjects. Mixing psyllium with the cereal or incorporating it into the cereal reduced the rate of digestion of bran flakes in vitro but was not associated with increased breath hydrogen levels in vivo as an index of rapid colonic fermentation. The bran flakes with psyllium incorporated was rated as no less palatable than the bran flakes cereal alone, and significantly more palatable (p less than 0.05) than taking psyllium in water before the cereal or sprinkling psyllium onto the cereal. These studies confirm earlier reports that viscous fibers must be intimately mixed with the food to have the effect of reducing blood glucose responses, and that the mechanism of action relates to a reduced rate of digestion rather than carbohydrate malabsorption.(ABSTRACT TRUNCATED AT 250 WORDS)

Construction of hybrid yeasts with increased flocculation for white wine manufacture

Abstract Hybrid strains of yeast have been selected that have better flocculating properties for white wine manufacture. The hybridisation of the production winemaking strain 13a (Varna 84) with a Saccharomyces cerevisiae haploid strain carrying the FLO5 mutation resulted in a hybrid with very good flocculation ability. Its fermentation activity was increased using several backcrosses. At the final step two meiotic segregants with mating ability were crossed with the production wine‐manufacturing strain 75b (Sofia 75); hybrids K93 and K97 were obtained. These hybrids showed better flocculation ability and a more rapid fermentation in comparison with the parental strains 13a and 75b. The composition, taste and aroma of wines obtained using hybrids were similar to those produced by parental strains. The treatment of young white wines was easier if constructed hybrid strains were used.

Rapid Ethanol Fermentation for Soy Sauce Production by Immobilized Yeast Cells.

Continuous ethanol fermentation was done to improve soy sauce productivity using immobilized soy sauce yeast cells. The yeast cells were immobilized physically in pores of alumina ceramic beads, and fermentation was done with a filtrate solution from soy sauce mash. The ethanol concentration was controlled by the dilution rate, and the volumetric production rate, being dependent on dilution rate, was found to be much higher than that in batch fermentation. The ethanol production system was mathematically modeled from the basic material balance and the rate equation. The simulated results agreed with the experimental ones. The reactor system with immobilized yeast cells was effective for obtaining ethanol with a high production rate.

Effect of lactulose on the metabolism of short-chain fatty acids

Short-chain (C2C5) fatty acids account for 60%–70% of the anions in the colon. Acetate (C2) is nontoxic in contrast to C(3)4C5 fatty acids (propionate, butyrate, isobutyrate, valerate, and isovalerate), which induce coma in animals and may be important in the pathogenesis of hepatic coma in humans. An in-vitro fecal incubation system was used to map out short-chain fatty acid production in the presence of lactulose, amino acids, albumin, or blood. Albumin and blood increased production of all C2C5 fatty acids. In contrast, lactulose was converted to acetate only and increased fecal acidity. The degradation of amino acids, albumin, and blood to short-chain fatty acids was completely inhibited by 10–25 mM lactulose. This was caused mainly by the acidifying effect of lactulose. pH-independent inhibition of blood and amino acid degradation to short-chain fatty acids required concentrations of lactulose exceeding 50–100 mM. Thus, the effect of lactulose in the treatment of hepatic coma may be related to its rapid fermentation into organic acids at rates exceeding colonic buffering capacity. This probably reduces formation of toxic fatty acids and ammonia from amino acids, polypeptides, and blood in the colon.

Experimental approaches to a rapid ethanol fermentation of glucose by aZymomonas mobilis strain

Rapid ethanol fermentation is defined as a fermentation in which the ethanol content increases from 0 to 94.8 g 1(-1) in 6 horless. To achieve this by the fermentation of glucose withZymomonas mobilis, the initial biomass concentration must be at least 20 g dry wt 1(-1) and that of the substrate must not exceed 150 to 200 g 1(-1) during fermentation. The best results were obtained with a medium containing initielly 16% of the total sugar with the remaining glucose being added continuously, after 20 min of incubation, over 5 h at a rate of 0.21 g/min. After 6 h, ethanol reached 102 g 1(-1), the volumetric productivity was 17g ethanol 1(-1) h(-1) and the yield 79.8 or 88% of the theoretical value, calculated according to the total fed or the consumed glucose, respectively.

Characterization of wild strains ofLactococcus lactissubsp.lactisisolated from Cabrales cheese

SummaryTwentyLactococcus lactissubsp.lactisstrains isolated from cheese made from raw milk have been, studied and compared with well known starter strains. Many of them produced acid bacteriocins resembling those of other lactic streptococci and their patterns of antimicrobial agent susceptibility were also similar to previously studied dairy strains. On the basis of their ability to clot milk they could be divided into two groups. Some strains were rapid fermenters, with highβ-phosphogalactosidase and proteolytic activities. The other group had lowβ-phosphogalactosidase activity and coagulated milk slowly, but seemed to have proteolytic activity. All the strains had plasmid DNA in amounts and sizes similar to starter strains. Aβ-phosphogalactosidase probe was constructed with plasmid DNA from aLc. lactissubsp.lactisNCDO 712 derivative. Southern hybridization located homologous sequences in chromosomal and plasmid DNA from the wild isolates that fermented lactose efficiently, but the degree of homology was lower than that observed between starter strains.

The degradation of amino acids, proteins, and blood to short-chain fatty acids in colon is prevented by lactulose

Short-chain (C2-C5) fatty acids account for 60%–70% of the anions in the colon. Acetate (C2) is nontoxic in contrast to C(3)4-C5 fatty acids (propionate, butyrate, isobutyrate, valerate, and isovalerate), which induce coma in animals and may be important in the pathogenesis of hepatic coma in humans. An in-vitro fecal incubation system was used to map out shortchain fatty acid production in the presence of lactulose, amino acids, albumin, or blood. Albumin and blood increased production of all C2-C5 fatty acids. In contrast, lactulose was converted to acetate only and increased fecal acidity. The degradation of amino acids, albumin, and blood to short-chain fatty acids was completely inhibited by 10–25 mM lactulose. This was caused mainly by the acidifying effect of lactulose. pH-independent inhibition of blood and amino acid degradation to short-chain fatty acids required concentrations of lactulose exceeding 50–100 mM. Thus, the effect of lactulose in the treatment of hepatic coma may be related to its rapid fermentation into organic acids at rates exceeding colonic buffering capacity. This probably reduces formation of toxic fatty acids and ammonia from amino acids, polypeptides, and blood in the colon.

Reasons for the apparent difference in the effects of produced and added ethanol on culture viability during rapid fermentation by Saccharomyces cerevisiae

By feeding ethanol at various high rates to low cell density cultures of Saccharomyces cerevisiae it was shown that the sharp fall in viability when ethanol is produced during rapid fermentations is in part a direct consequence of the high rate of change of extracellular ethanol concentration. Nevertheless, the fall in viability in high cell density rapid fermentations which produced 98 g L(-1) ethanol in 3 h considerably exceeded that of control low cell density cultures to which ethanol was added at the same rate. This difference was shown to be not due to intracellular ethanol accumulation or to differences in glucose concentration between the cultures. The concentrations of a range of potentially toxic fatty acids, higher alcohols, and esters were measured during rapid fermentations, but when added at these concentrations to control cultures in the presence of ethanol they had no significant toxic effect. However, when rapid fermentations were conducted in rich medium containing 80 g L(-1) yeast extract, the apparent difference in toxicity of produced and added ethanol virtually disappeared. Magnesium was shown to be the component of yeast extract primarily responsible for this effect. The high rate of fall of viability when ethanol is rapidly produced is suggested to be partly due to the inability of the cells to adapt quickly enough to the rising ethanol concentration and partly to an increased demand for magnesium at higher ethanol concentrations which cannot be met in Mg-unsupplemented high cell density fermentations.

Feeding antibiotic-contaminated waste milk to calves—Effects on physical performance and antibiotic sensitivity of gut flora

The effect of feeding calves antibiotic-containing waste milk was studied in two trials. In the first trial both fermented and unfermented waste milk were fed and in the second trial only unfermented milk was used. The antibiotic-containing milk had a poor palatability and rejection rates were high. Growth rates of the calves were poor and in the second trial differed significantly from those of the control calves which had received milk substitute. Faecal E. coli were monitored for antibiotic resistance. In the first trial, the geometric mean minimal inhibitory concentration for streptomycin was significantly higher for isolations from calves fed antibiotic-containing milk, but no differences were observed for ampicillin. In the second trial, the percentage of resistant E. coli and enterococci was determined but no differences were observed between isolations from calves fed antibiotic-containing milk and the controls. The ambient conditions in the United Kingdom did not encourage the rapid natural fermentation, which would degrade the antibiotics and make it an acceptable food, and it was concluded that the high numbers of bacteria in the product may present disease risk.

Monoclonal Antibody Direct Immunofluorescence for the Identification of Neisseria gonorrhoeae Strains Grown on Selective Culture Media

Commercially available reagents for monoclonal antibody immunofluorescence, polyclonal antibody immunofluorescence, and coagglutination were employed in comparison with a rapid sugar fermentation test used for identifying clinical isolates of Neisseria gonorrhoeae recovered on modified Thayer-Martin media. Of 68 gonococcal strains, 68 were positive by the monoclonal immunofluorescent antibody. Of 16 nongonococcal gram-negative, oxidase-positive diplococci, all were negative by this reagent. Monoclonal antibody immunofluorescence was more specific and more sensitive than polyclonal antibody immunofluorescence and more sensitive than coagglutination.

Evaluation of thermotolerant yeasts in controlled simultaneous saccharifications and fermentations of cellulose to ethanol

Simultaneous saccharification and fermentation (SSF) experiments were performed at selected temperatures (37, 41, and 43 degrees C) to obtain comprehensive material balance and performance data for several promising strains of thermotolerant yeast. Parameters measured were ethanol concentration, yeast cell density, and residual sugar and cellulose concentrations. The three yeasts Saccharomyces uvarum, Candida brassicae, and C. lusitaniae and two mixed cultures of Brettanomyces clausenii with S. cerevisiae (mixed culture I) and C. Iusitaniae with S. uvarum (mixed culture II) exhibited rapid rates of fermentation, high ethanol yields, strong viability, or high cellobiase activity. Overall, mixed culture II at 41 degrees C performed better than either component yeast by themselves because it combined a cellobiose fermenting capability with the high ethanol tolerance and rapid glucose fermentation of conventional industrial yeasts. Thus, the mixed cultures provide good initial rates by preventing buildup of cellobiose (a strong inhibitor of enzyme activity) while attaining high ultimate yields of ethanol for high cellulase concentrations. However, C. brassicae and S. uvarum gave similar results to mixed culture II at 37 degrees C.

Utilization of alpha-amylase (EC 3.2.1.1) resistant maize and pea (Pisum sativum) starch in the rat.

1. The extent of utilization of alpha-amylase (EC 3.2.1.1)-resistant retrograded starches in vivo was assessed in male Wistar rats (about 100 g body-weight). All animals were given a fibre-free semi-synthetic basal diet (SS) containing sucrose as the only carbohydrate source, ad lib., for 13 d. On day 14, after an overnight fast, rats were allocated to one of five dietary treatments (n 30):1, fibre-free basal SS diet; 2-5, basal SS diet supplemented with 100 g sucrose, Solka floc (cellulose), resistant maize starch (RCS) or resistant pea (Pisum sativum) starch (RPS)/kg diet. Animals allocated to each dietary treatment were divided into three groups of ten rats which were given the appropriate diet for 8 or 9, 17 or 18 and 29 or 30 d (8/9, 17/18 or 29/30 d groups respectively). Rats were fed on 12 g diet/d (treatment 1) or 13.2 g diet/d (treatments 2-5) for the first 20 d, and 14 or 15.4 g/d respectively until the end of the experiment. Rats fed on the supplemented basal diets were thus given 10% more food to allow for the addition of the test carbohydrate. Faecal carbohydrate excretion was determined at intervals in the 17/18 d groups. At the end of each experimental period animals were killed after consuming their daily food ration and small intestinal length, weight of caecal and ileal contents and tissue, and pH of caecal contents measured. The amount of carbohydrate in the caecal and ileal contents from the 8/9 and 17/18 d groups was determined. 2. Weights of ileal and caecal contents, caecal tissue and faecal output were significantly greater at all time points for rats fed on the resistant starches compared with those fed on basal and sucrose-supplemented diets. Values were higher for RPS-fed rats than for RCS-fed rats. 3. The quantity of carbohydrate recovered from ileal and caecal contents showed that both RCS and RPS were partially digested and absorbed as carbohydrate, but that RPS was digested to a lesser extent. 4. The concentration of carbohydrate decreased between the ileal and caecal sites when RPS and RCS were given but was essentially unchanged when cellulose was given. This is consistent with rapid fermentation of a fraction of these starches. 5. Faecal carbohydrate elimination in the 17/18 d groups fed on RCS and RPS declined with time, which suggested an adaptive response resulting in increased utilization of the starches. This adaptive response was slower in the RPS-fed rats than the RCS-fed rats.(ABSTRACT TRUNCATED AT 400 WORDS)

In Vitro Fermentabilities of Purified Fiber Supplements

ABSTRACTSix commonly used dietary fiber supplements (pectin, tragacanth gum, psyllium gum, guar gum, soy fiber and cellulose) were fermented in vitro with human fecal microbiota for 4, 8,12, and 24 hr. Short chain fatty acids (SCFA), hydrogen and methane productions, and neutral‐detergent fiber digestibility differed significantly with fiber source. The most rapid fermentation rate was with pectin followed by psyllium gum, tragacanth gum, guar gum, soy fiber, and finally cellulose. Such differences in fermentability should be considered when food products are formulated. Dietary fiber source and intake may also affect breath hydrogen measurements and estimates of available carbohydrate malabsorption.

Lamb performance on swedes supplemented with barley or soya bean meal

Supplementation of finishing lambs fed swedes in situ has been traditionally achieved with cereals or 14% CP compound feeds. Crowing of winter cereals has reduced the availability of protein-rich grass runbacks and on most farms where lambs are consuming mainly swede bulbs there is likely to be a daily deficit of RDP of around 16 g RDP/day (0.15 of total requirement). Recent MLURI work (Milne pers comm) indicates that the normal RDP:ME ratio of ruminant diets of 7.8:1 may be inadequate in the unusual conditions of high rumen turnover rates and rapid fermentation associated with root feeding. Rowett feed evaluation work indicates higher ME values for swedes than previous estimates increasing energy:protein imbalance.This trial had two objectives; to study response to supplementation of swedes with soya bean meal compared to barley and to study whether holding lambs for 3 months inside on a straw based diet prior to finishing was an effective alternative to holding lambs on autumn grass outside. The potential advantages of this alternative are reduced competition for autumn grass between breeding ewes and finishing stock and better utilisation of sheep housing and arable by-products.

Ethanol and butanol production by fermentation of enzymatically saccharified SO 2-prehydrolysed lignocellulosics

The present paper reports the results of SO 2-catalysed prehydrolysis of lignocellulosics, namely pine, aspen, and corn stover, and their direct saccharification, without washing, by cellulolytic enzymes to produce a mixture of hemicellulose and cellulose sugars. Total sugar yield upon enzymatic hydrolysis of these prehydrolysed residues was over 65% of the weight of raw material, or above 86% of theoretical yields. Fermentation by a strain of Pichia stipitis adapted to wood hydrolysates by recycling, designated the R strain, resulted in efficient utilization of xylose, high ethanol yields, and good tolerance of inhibitors. Fermentation of hydrolysates containing both the hemicellulose and cellulose sugars by P. stipitis R gave yields of 372, 346, and 388 l ethanol tonne −1 (dry weight of prehydrolysed feedstock) from pine, aspen, and corn stover, respectively. These yields represent over 74% of theoretical. Extractive fermentation of these hydrolysates to acetone-butanol-ethanol by Clostridium acetobutylicum P262 using dibutylphthalate as in situ extractant in a semicontinuous mode resulted in rapid fermentation, when using a high cell concentration and recycling the cells for each 24-h fermentation to the succeeding batch. By this means, 255 l of acetone-butanol solvents were obtained per tonne of aspen, 298 l per tonne of pine, and 283 l per tonne of corn stover. The technical aspects of prehydrolysis using SO 2 catalyst, enzymatic saccharification, the advantages of using P. stipitis R for the fermentation of pentose-rich hydrolysates, and the potential of dibutylphthalate for extractive fermentation to obtain high yields of solvents are discussed.

Regulation of sugar transport and metabolism in lactic acid bacteria

The phosphoenolpyruvate (PEP)-dependent lactose: phosphotransferase system (PTS), P-β-galactosidase, and enzymes of the d-tagatose-6P pathway, are prerequisite for rapid homolactic fermentation of lactose by Group N (‘starter’) streptococci. Moreover, the reactions of transport and catabolism constitute an open cycle in which ATP and lactic acid are metabolic products. The efficient and controlled operation of this cycle requires ‘fine-control’ mechanisms to ensure: (i) tight coupling between transport and energy-yielding reactions, (ii) co-metabolism of both glucose and galactose moieties of the disaccharide, and (iii) coordination of the rate of sugar transport to the rate of sugar catabolism. The elucidation of these fine-control mechanisms in intact cells of Streptococcus lactis has required the isolation of glucokinase (GK) and mannose-PTS defective mutants, the synthesis of novel lactose analogs, and the use of high resolution [ 31P]NMR spectroscopy. It has been established that PEP provides the crucial link between transport and energy-yielding reactions of the PTS: glycolysis cycle, and that both ATP-dependent glucokinase and PEP-dependent mannose-PTS can participate in the phosphorylation of intracellular glucose. Finally, evidence has been obtained in vivo, for modulation of pyruvate kinase activity in response to fluctuation in, concentrations of positive (FDP), and negative (P i) effectors of the allosteric enzyme. Fine-control of pyruvate kinase activity may in turn regulate: (i) the distribution of PEP to either the PTS or ATP synthesis, (ii) overall activity of the PTS: glycolysis cycle, and (iii) the formation of the endogenous PEP-potential in starved organisms. The accumulation of non-metabolizable PTS sugars (e.g., 2-deoxy- d-glucose) by growing cells can perturb these fine-control mechanisms and, by establishment of a PEP-dissipating futile cycle, may result in bacteriostasis.

Regulation of sugar transport and metabolism in lactic acid bacteria

Abstract The phosphoenolpyruvate (PEP)-dependent lactose: phosphotransferase system (PTS), P-β-galactosidase, and enzymes of the d -tagatose-6P pathway, are prerequisite for rapid homolactic fermentation of lactose by Group N (‘starter’) streptococci. Moreover, the reactions of transport and catabolism constitute an open cycle in which ATP and lactic acid are metabolic products. The efficient and controlled operation of this cycle requires ‘fine-control’ mechanisms to ensure: (i) tight coupling between transport and energy-yielding reactions, (ii) co-metabolism of both glucose and galactose moieties of the disaccharide, and (iii) coordination of the rate of sugar transport to the rate of sugar catabolism. The elucidation of these fine-control mechanisms in intact cells of Streptococcus lactis has required the isolation of glucokinase (GK) and mannose-PTS defective mutants, the synthesis of novel lactose analogs, and the use of high resolution [ 31 P]NMR spectroscopy. It has been established that PEP provides the crucial link between transport and energy-yielding reactions of the PTS: glycolysis cycle, and that both ATP-dependent glucokinase and PEP-dependent mannose-PTS can participate in the phosphorylation of intracellular glucose. Finally, evidence has been obtained in vivo, for modulation of pyruvate kinase activity in response to fluctuation in, concentrations of positive (FDP), and negative (P i ) effectors of the allosteric enzyme. Fine-control of pyruvate kinase activity may in turn regulate: (i) the distribution of PEP to either the PTS or ATP synthesis, (ii) overall activity of the PTS: glycolysis cycle, and (iii) the formation of the endogenous PEP-potential in starved organisms. The accumulation of non-metabolizable PTS sugars (e.g., 2-deoxy- d -glucose) by growing cells can perturb these fine-control mechanisms and, by establishment of a PEP-dissipating futile cycle, may result in bacteriostasis.