OPTIMIZATION OF THE LACTIC ACID FERMENTATION OF HYDROLYZED COD (GADUS MORHUA) GURRY WITH CORN SYRUP AS CARBOHYDRATE SOURCE

ABSTRACT The purpose of this study was to determine the optimum concentrations of corn syrup required with the use of several species of homofermentative lactic acid bacteria and a commercial mixed culture inoculum in the fermentation of hydrolyzed cod gurry. Among the three homofermentative bacteria studied, Lactobacillus plantarum, Streptococcus faecium, and Pediococcus acidilactici, consistent results regarding the most rapid rate of pH reduction and the lowest final pH were obtained with L. plantarum. S. faecium was the least desirable organism on the basis of fermentation rates and the extent of pH reduction after 72 h of incubation. Corn syrup at a concentration of 4.0% (w/w) was found to be optimum for achieving a rapid and successful lactic acid fermentation of hydrolyzed cod gurry with Lactobacillus plantarum. Corn syrup at a concentration of 4.5% was found to be optimum for rapidly achieving a final pH of 4.0 with the commercial mixed inoculum Stabisil. The maltose content of corn syrup was utilized at a notably slower rate than glucose by all three microorganisms during the first 18 h of incubation. Throughout the fermentations, maltotriose was utilized significantly by only L. plantarum.     

ACTIVITIES OF CERTAIN AMINOTRANSFERASES AND NADP-DEPENDENT GLUTAMIC ACID DEHYDROGENASE IN YEAST DURING FERMENTATION

The activities of alanine (E.C.2.6.I.2.), aspartate (E.C.2.6.I.I) and glycine (E.C. 2.6.I.4) aminotransferases and NADP-dependent glutamic acid dehydrogenase (E.C.I.4.I.4) have been followed in Saccharomyces cerevisiae during fermentation in an all-malt wort. The synthesis of alanine aminotransferase is enough to furnish the yeast with alanine, but glycine aminotransferase activity is inadequate for glycine requirements during the fermentation period when glycine and alanine are not assimilated from the medium. The synthesis of all four enzymes is repressed to various extents during the early stages of fermentation, but de-repression occurs towards the end of the fermentation.     

紫外分光光度法测定发酵液中克拉维酸含量的研究

利用克拉维酸与咪唑的衍生物在312nm下具有特征吸收的原理对其含量进行测定，回收率为99．1％～101．7％，衍生后的克拉维酸稳定性较好，增加了测量的准确性，并与高效液相色谱法进行了比较，实验表明该方法具有准确、简便、快速、操作系统简单等特点，对于成品及半成品两种方法测定结果一致，是一种用于检测发酵液中克拉维酸含量的简便、快捷的方法。     

FERMENTATION OF SYNTHETIC MEDIA CONTAINING GLUCOSE AND MALTOSE BY BREWER'S YEAST

Brewer's yeast previously cultured on either glucose or maltose as the sole source of carbohydrate has a period of exclusive utilization of glucose when grown on synthetic media containing glucose and maltose. Only when glucose has fallen to a low level does fermentation of maltose begin. This behaviour is thought to be due to an effect of glucose on the maltose permease.     

LONG-CHAIN FATTY ACID COMPOSITION AS A CRITERION FOR YEAST DISTINCTION IN THE BREWING INDUSTRY

The diversity of yeasts isolated from brewing plants and its role on beer quality makes yeast distinction a major concern in industrial microbiological control. Several approaches have been tried to develop rapid and simple methods to perform such tasks. Among these, stands the utilization of long-chain fatty acid composition of total yeast biomass. In this paper results are reported showing the potential of this technique to characterize yeast flora isolated from industrial plants. Fatty acid profiles of brewing species are clearly differentiated from those of non-Saccharomyces strains using statistical data treatment by principal component analysis (PCA). Distinction between brewing and wild strains of Saccharomyces spp. was not apparent. In comparison, fatty acid profiling showed higher discriminating ability than growth on lysine medium for non-Saccharomyces strains. For distinction of S. cerevisiae var. diastaticus from other Saccharomyces strains, growth on starch medium showed to be necessary.     

FERMENTATION PROPERTIES OF BREWING YEAST WITH KILLER CHARACTER

The cytoplasmically-inherited killer character of a laboratory strain of Saccharomyces cerevisiae has been transferred to three different commercially-used brewing yeasts; two ale strains and one lager strain. The ease with which the character can be transferred is very strain dependent. In addition to killer character, mitochondria from the brewing strain have been transferred into the new ‘killer’ brewing strains. Fermentations carried out with the manipulated strains produced beers which were very similar to those produced by the control brewing strains. The beers produced by killer brewing strains containing brewing yeast mitochondria were most like the control beers and could not be distinguished from them in three glass taste tests. In addition to producing good beers the genetically manipulated yeasts killed a range of contaminant yeasts and were themselves immune to the action of Kil-k₁ killer yeasts.     

CONTINUOUS FERMENTATION IN RELATION TO YEAST METABOLISM

In homogeneous systems for the continuous fermentation of wort by Saccharomyces cerevsiae fluctuations often occur in the ability of cells to remove and ferment sugars even under steady-state conditions. In partially closed systems of this type where high concentrations of yeast are accumulated and growth is suppressed, such fluctuations are magnified. The results of these fluctuations are demonstrated and the causes and results of a simultaneous decline in the rate of removal and fermentation of maltose are discussed. Such undesirable effects are largely eliminated by the use of a system which incorporates at least two stages and a continuous fermentor of such a design has operated with a high degree of stability at dilution rates as high as 0·4 h^?1.     

AMINO ACID CHANGES IN THE KOREAN TRADITIONAL FERMENTATION PROCESS FOR BLUE MUSSEL, MYTILUS EDULIS

The effect of fermentation period on biochemical composition of fermented blue mussel was investigated in three fermentation stages. Fermented blue mussel sauces (FBMSs) were prepared with 25% NaCl (w/w) at 20C for different fermentation periods. The FBMSs were desalted below 1% (w/w) by an electrodialyzer. It was observed that content of protein increased and carbohydrate decreased throughout the fermentation. In addition, the changes of free amino acids were investigated, and the levels of amino acids such as glycine, alanine, proline, aspartic acid and glutamic acid were higher, which may be important for the taste of fish and shellfish sauce.     

AMINO ACID ESTERS IN BEER

The ethyl esters of valine, leucine and iso-leucine have been detected in a range of commercial and experimental beers at levels between ca. 3 ppb and 71 ppb. However these compounds have been shown to have no noticeable effect on beer flavour at levels up to at least 12 ppm.     

REDUCTION OF HIGHER ALCOHOLS BY FERMENTATION WITH A LEUCINE-AUXOTROPHIC MUTANT OF WINE YEAST

Several auxotrophic mutants requiring branched chain amino acids (valine, leucine, or isoleucine) were isolated in a strain of Montrachet wine yeast. They were tested for their ability to produce lowered amounts of higher alcohols (‘fusel oil’: isobutyl, active amyl, and isoamyl alcohols) in grape juice fermentations. One strain which required leucine was especially good in this respect. This mutation is recessive and is the result of a deficiency for the enzyme α-isopropylamate dehydratase. In trial fermentations with this mutant, the resulting wines contained up to 20% less total fusel oil and 50% less isoamyl alcohol compared to the parent Montrachet strain. An experienced taste panel did not discern any gross degradation of taste quality in wine made with the mutant strain compared to that made with the parent strain. The mutant strain could be of commercial importance in preparation of distilling material for alcoholic beverages since the reduced fusel oil content would not require any special distillation procedures which are normally used to avoid the unpleasant flavour associated with concentrated higher alcohols. Reduction of the isoamyl alcohol content is particularly significant since this fusel oil component is usually present in the highest amount.     

KH2PO4和复合氨基酸对乳链菌肽发酵的影响

在自然pH和恒pH培养条件下,研究乳链茵肽发酵培养基中的KH2PO4和复合氨基酸对细胞生长和乳链茵肽合成的影响.研究结果表明,KH2PO4在发酵液中主要起缓冲作用,最佳用量为由23 g/L降到15 g/L;原发酵培养剂中的氮源添加量减少50%,再添加10 g/L的复合氨基酸粉,发酵液的效价由4200IU/mL提高到6946 IU/mL,固含量由6.312g/L降到3.334g/L,颜色由棕黄色变成淡黄色.     

ESTIMATION OF AMINO NITROGEN IN WORTS AND BEERS USING EITHER NINHYDRIN OR 2,4,6-TRINITROBENZENE-1-SULPHONIC ACID

Colorimetric methods of estimating amino nitrogen have been calibrated, taking either glycine or leucine as the standard, and used to measure the amino nitrogen contents of worts and beers. Comparison of the 2,4,6-trinitrobenzene-1-sulphonic acid method with the ninhydrin procedure shows that amino nitrogen values differing by up to 15–20% can be obtained for the same sample and moreover that worts behave differently from beers.     

快速发酵面包酵母菌株的选育

对出发菌株进行紫外-氯化锂复合诱变，通过初筛、复筛选育出高麦芽糖发酵力、低葡萄糖阻遏的面包酵母菌株BM-72，该菌株在不加糖、低糖面团中均表现出较好的发酵力，分别高于出发菌株19．4％和7．3％。     

METHIONINE AND SULPHATE AS COMPETING AND COMPLEMENTARY SOURCES OF SULPHUR FOR YEAST DURING FERMENTATION

Study of the uptake of sulphate and methionine by an ale yeast from a range of media showed that utilisation of sulphate was fairly strictly controlled but assimilation of methionine was not. Cells never took up more than about 0.3 mMol sulphate per litre whilst methionine, up to an initial concentration of 10 mMol per litre, was completely absorbed. Sulphate-grown cells had low intracellular pools of amino acids and methinonine was never detected. Methionine-grown cells contained methionine in both cytosol and vacuole and the concentration of several other amino acids also increased in such a way to suggest that methionine catabolism was occurring. With mixed sulphur sources methionine prevented uptake of sulphate when the concentration of sulphate was high but not when it was low suggesting the presence of two sulphate transporters with different control properties. Sulphate did not influence uptake of methionine. Addition of other amino acids to the medium did reduce the rate and extent of methionine uptake but not the intracellular pool sizes. Pilot plant studies suggested that SO₂ production in a brewery is more likely to be a reflection of the overall nutritive status of the wort rather than be connected to the initial methionine concentration .     

STUDIES IN CONTINUOUS FERMENTATION I. EFFECTS OF YEAST CONCENTRATION

Saccharomyces cerevisiae (NCYC 1026) was grown in synthetic medium, brewer's wort and media intermediate in composition, using both open and closed systems of continuous culture. The level of nitrogen source in the synthetic medium severely restricted growth in the open system but with similar flow-rates in the closed system much higher yeast populations were maintained. The levels of the ethanol and fusel alcohols in the spent media were not, however, commensurate with the difference in cell numbers but the total fusel alcohol production at higher yeast concentrations was about five times as great and that of ethanol was two-fold. With wort or an intermediate medium, the level of assimilable nitrogen was greater and in the closed system some of the nitrogen, particularly proline, was not utilized. Proline uptake was stimulated by increasing the level of carbohydrate in the medium or by increasing aeration so that more carbohydrate was diverted into metabolic pathways associated with growth rather than fermentation.