利用啤酒废酵母制备富锌酵母

以啤酒废酵母为原料制备富锌酵母.对制备的工艺条件进行了优化.确定最佳的工艺条件条件为:Zn2+的浓度为500μg/mL;培养pH值为4.5:振荡培养时间为10h;啤酒酵母投加量为50g/50mL培养基.通过红外分析对空白废酵母和富锌废酵母进行比较,分析了酵母富集锌前后吸收峰的变化.     

Identification of regulatory elements in the AGT1 promoter of ale and lager strains of brewer's yeast

Agt1 is an interesting α-glucoside transporter for the brewing industry, as it efficiently transports maltotriose, a sugar often remaining partly unused during beer fermentation. It has been shown that on maltose the expression level of AGT1 is much higher in ale strains than in lager strains, and that glucose represses the expression, particularly in the ale strains. In the present study the regulatory elements of the AGT1 promoter of one ale and two lager strains were identified by computational methods. Promoter regions up to 1.9 kbp upstream of the AGT1 gene were sequenced from the three brewer's yeast strains and the laboratory yeast strain CEN.PK-1D. The promoter sequence of the laboratory strain was identical to the AGT1 promoter of strain S288c of the Saccharomyces Genome Database, whereas the promoter sequences of the industrial strains diverged markedly from the S288c strain. The AGT1 promoter regions of the ale and lager strains were for the most part identical to each other, except for one 22 bp deletion and two 94 and 95 bp insertions in the ale strain. Computational analyses of promoter elements revealed that the promoter sequences contained several Mig1- and MAL-activator binding sites, as was expected. However, some of the Mig1 and MAL-activator binding sites were located on the two insertions of the ale strain, and thus offered a plausible explanation for the different expression pattern of the AGT1 gene in the ale strains. Accordingly, functional analysis of A60 ale and A15 lager strain AGT1 promoters fused to GFP (encoding the green fluorescent protein) showed a significant difference in the ability of these two promoters to drive GFP expression. Under the control of the AGT1 promoter of the ale strain the emergence of GFP was strongly induced by maltose, whereas only a low level of GFP was detected with the construct carrying the AGT1 promoter of the lager strain. Thus, the extra MAL-activator binding element, present in the AGT1 promoter of the ale strain, appears to be necessary to reach a high level of induction by maltose. Both AGT1 promoters were repressed by glucose but their derepression was different, possibly due to a distinct distribution of Mig1 elements in these two promoters.     

Debittering of spent brewer's yeast for food purposes

The analysis of spent brewer's yeast slurry exhibited a five-day biochemical oxygen demand (B.O.D.) of 158 400 mg/l at 20% yeast concentration. A treatment process for debittering was tried. The steps include removal of extraneous materials, reduction of the viscosity of slurry, debittering the yeast cells and centrifuging, washing and drying the debittered yeast-cell biomass in a drum dryer. Debittering was carried out successfully by adjusting the pH and temperature of the slurry. pH 10 at 50 °C of the slurry resulted in the complete debittering of the yeast-cells in a single treatment without affecting the chemical and essential amino acid compositions.     

Advances in the valorization of spent brewer's yeast

Spent brewer's yeast (SBY) is one of the major by-products produced during beer brewing process. SBY is an abundant source of protein, minerals, vitamins, especially vitamin Bcomplex, as well as nutraceuticals such as β-glucans or mono- and oligosaccharides. Due to the presence of nutrients, abundant availability and low cost, SBY has been widely used in animal feed. However, over the last decades, considerable efforts have been devoted to the development of alternative applications for SBY, such as functional food ingredient and fermentation substrate. Therefore, the aim of this review was to provide an up-to-date overview on the valorization of SBY.     

Beer brewing using a fusant between a sake yeast and a brewer's yeast

Beer brewing using a fusant between a sake yeast (a lysine auxotrophic mutant of sake yeast K-14) and a brewer's yeast (a respiratory-deficient mutant of the top fermentation yeast NCYC1333) was performed to take advantage of the beneficial characteristics of sake yeasts, i.e., the high productivity of esters, high tolerance to ethanol, and high osmotolerance. The fusant (F-32) obtained was different from the parental yeasts regarding, for example, the assimilation of carbon sources and tolerance to ethanol. A brewing trial with the fusant was carried out using a 100-l pilot-scale plant. The fusant fermented wort more rapidly than the parental brewer's yeast. However, the sedimentation capacity of the fusant was relatively low. The beer brewed using the fusant contained more ethanol and esters compared to that brewed using the parental brewer's yeast. The fusant also obtained osmotolerance in the fermentation of maltose and fermented high-gravity wort well.     

Determinants of flocculence of brewer's yeast during fermentation in wort

Ability of Saccharomyces cerevisiae MPY3 cells to flocculate during fermentation in wort was found to be triggered after growth limitation by oxygen shortage and to coincide with a sharp increase in cell surface hydrophobicity of the cells. Presence of oxygen in the pitching wort influenced final cell number, flocculence of the cells and cell surface hydrophobicity. Flocculation ability of cells grown in air-depleted pitching wort was hampered, concomitant with a decrease in final cell number and in final cell surface hydrophobicity. Addition of ergosterol and Tween 80 to air-depleted wort restored normal growth of the cells as well as flocculation ability and the increase in cell surface hydrophobicity. The same parameters increased in value after addition of ergosterol and Tween 80 to a fermentation with air-saturated pitching wort. Hydrophobicity of a non-flocculent mutant of S. cerevisiae strain MPY3, fermenting in air-saturated pitching wort, did not increase at cell division arrest. These results support the hypothesis that cell surface hydrophobicity is a major determinant for yeast cells to become flocculent, and suggest that shortage of sterols and unsaturated fatty acids precedes flocculence under brewing conditions.     

Breeding of brewer's yeast by hybridization between a top-fermenting yeast Saccharomyces cerevisiae and a cryophilic yeast Saccharomyces bayanus

To improve the fermentability of a top-fermenting yeast at low-temperature, we performed hybridization trials between four top-fermenting Saccharomyces cerevisiae strains and a cryophilic yeast Saccharomyces bayanus YM84 with good fermentability at low-temperature. The hybrids selected using 5-bromo-4-chloro-3-indolyl-alpha-D-galactopyranoside were checked with pulsed-field gel electrophoresis and their brewing performance at the low-temperature of 10.5 degrees C was observed using small-scale (2 l) fermentation trials.     

利用有活力和无活力的啤酒废酵母生产酵母抽提物

以两种形态的啤酒废酵母(有活力的和无活力的)为原料,制备酵母抽提物。实验表明,采用自溶法处理啤酒废酵母液(有活力的),最佳作用条件是在温度45℃、pH 5.5下,自溶28 h,所得酵母抽提液的氨基氮含量为5.16 g/L,氨基氮得率为6.77%,产品得率为69.01%;酶采用酶水解法添加木瓜蛋白处理啤酒废酵母粉(无活力的),最佳作用条件是在木瓜蛋白酶添加量2.5%(以酵母干重计)、温度55℃p、H 4.5下,酶水解时间18 h,所得酵母抽提液的氨基氮含量为3.35 g/L,氨基氮得率为4.31%,产品得率为76.66%。     

低产乙醛啤酒酵母的定向驯化筛选

为降低啤酒中乙醛含量,采用紫外线对1株啤酒工业生产菌株MI4进行诱变,经双硫仑平板初筛、乙醛培养基驯化复筛,获得了1株低产乙醛的啤酒酵母D-A-14。与出发菌株MI4相比,采用该突变株酿制的啤酒中乙醛含量为2.86 mg/L,降低了76%;且高级醇总量降低而酯含量升高,风味更加协调。这表明筛选得到的低乙醛突变株适于啤酒工业生产。     

The influence of calcium-carbonate and yeast extract addition on lactic acid fermentation of brewer's spent grain hydrolysate

Brewer's spent grain (BSG) is the major by-product of the brewing industry, representing around 85% of the total by-products generated. In this study BSG hydrolysate was produced using optimal conditions. Hydrolysates were used for lactic acid (LA) fermentation by Lactobacillus fermentum (PL-1) and Lactobacillus rhamnosus (ATCC 7469). The aim of this study was to evaluate possibilities of the BSG hydrolysate utilization as a substrate for LA fermentation. The effect of calcium-carbonate (2%) and yeast extract (0.5 to 5%) addition in hydrolysate on LA fermentation were investigated. The LA production by L. fermentum and L. rhamnosus in BSG hydrolysate was influenced by calcium-carbonate and yeast extract supplementation. L. fermentum produced a racemic mixture of L-(+)- and D-(−)-LA while L. rhamnosus produced mostly L-(+)-LA (95–98%) in all fermentations. Calcium-carbonate addition increased total LA yield by 13% in L. fermentum fermentations and by 17% in L. rhamnosus fermentations. Yeast extract addition increased total LA yield by 4–26% in L. fermentum fermentations and by 6–8% in L. rhamnosus fermentations.     

Isolation and partial purification of mannose-specific agglutinin from brewer's yeast involved in flocculation

Yeast cell-agglutinating activity, designated agglutinin (possible lectin), was isolated from cell walls of both non-flocculent and flocculent brewer's yeast cells. Agglutinin-mediated aggregation of yeast cells in a manner similar to flocculation with respect to specific mannose-sensitivity, pH-dependence and calcium-dependence. Agglutinating activity was found to be heat-stable and protease-insensitive. Furthermore, addition of agglutinin to flocculent cells strongly stimulated the flocculation ability of the cells, whereas addition to non-flocculent cells rendered these cells weakly flocculent. Agglutinin was found to be released from flocculent cells during the course of a flocculation assay, but not from non-flocculent cells. Presence of mannose during the assay inhibited release of agglutinin. Our results suggest that (i) mannose-specific agglutinin is continuously synthesized during growth of brewer's yeast cells, (ii) agglutinin is present in cell walls of non-flocculent cells but is unable to bind its ligand on other cells, and (iii) the ability of yeast cells to flocculate in a flocculation assay depends, among other factors, on release of agglutinin from the cells. A 10-kDa polypeptide might represent one form of agglutinin.     

酿酒废酵母吸附共存重金属离子的研究

为研究酿酒废酵母吸附共存重金属离子的可行性,在单因素试验的基础上,采用响应曲面法探讨酿酒废酵母吸附共存离子Pb2+、Ni 2+、Cu2+的最佳工艺条件。结果表明:酿酒废酵母对共存重金属离子Pb2+、Ni 2+、Cu2+吸附的最佳条件为pH值3.15,吸附温度30℃,吸附时间60min,酵母浓度2.04g/L,离子浓度61.34mg/L,该条件下酿酒废酵母对共存离子的吸附率为62.78%。     

Effects of soy protein hydrolysates on the growth and fermentation performances of brewer's yeast

Soy protein isolate was hydrolysed with Alcalase, Papain, Flavorzyme and Protemax, respectively, and further fractioned by ultrafiltration. The resulting soy protein hydrolysates (SPH) and their ultrafiltration fractions were used to examine their effects on the growth and fermentation performances of brewer's yeast. Results showed that degree of hydrolysis, molecular weight distribution and amino acid composition of SPH significantly affected the growth, viability and fermentation performance of brewer's yeast. The SPH prepared from different proteolytic enzymes exhibited distinct growth‐ and fermentation‐promoting activity for brewer's yeast. The SPH treated with Protemax for 9 h and with the molecular weight below 3 kDa showed the highest growth‐promoting activity and induced more rapidly reducing sugar consumption and higher ethanol production. The relatively lower molecular weight and the hydrophilic and electropositive amino acid residues (Lys, His, Arg and Ile) in SPH might be responsible for its functionality, promoting the growth and fermentation of brewer's yeast.     

A rapid and selective assay for measuring cell surface hydrophobicity of brewer's yeast cells

A rapid and selective assay was developed to measure cell surface hydrophobicity of brewer's yeast cells. During this so-called magnobead assay, bottom-fermenting yeast cells adhere to paramagnetic, polystyrene-coated latex beads which can easily be removed from the cell suspension by using a (samarium-cobalt) magnet. At pH 4·5, electrostatic repulsion between yeast cells and latex beads was found to be minimal and yeast cell adhesion was predominantly based on hydrophobic interactions. The percentage of cells adhering to the beads could be calculated and provided a measure for cell surface hydrophobicity. Cell surface hydrophobicity measured by the magnobead assay was found to yield similar results, as did determination of contact angles of water droplets on a layer of yeast cells, a standard method for measuring surface hydrophobicity. However, the magnobead assay has the following advantages: (i) it is a quick and simple method, and, more significantly, (ii) hydrophobicity can be measured under physiological conditions. Use of the magnobead assay confirmed that a higher level of cell surface hydrophobicity is correlated with stronger flocculence of brewer's lager yeast cells.     

不同氮源组成麦汁对酿酒酵母发酵性能的影响

研究了酿酒酵母Saccharomyces pastorianus(FBY0095)在六种不同氮源组成麦汁(20°P)中生物量、表观发酵度、乙醇浓度以及游离氨基氮(FAN)消耗量等指标的差异。结果表明,在20°P超高浓麦汁发酵中,麦汁氮源含量和组成对酵母发酵性能具有显著影响。随着麦汁中可同化氮量的提高,加速了酵母对糖的吸收利用,提高了酵母稳定期生物量和乙醇产量,发酵时间缩短了20%。当氮源匮乏(约为FAN=124.59 mg/L)时,补充适量大豆分离蛋白水解物(SPIH)于超高浓麦汁中,增加了麦汁氮源的多样性,使菌体增长量提高8.3%,乙醇产量提高4.43%,是酵母生长的有效氮源。      

Use of spent brewer's yeast in L‐(+) lactic acid fermentation

The application of by‐products from the brewing industry in lactic acid (LA) production was investigated in order to replace expensive nitrogen sources (such as yeast extract) with cheaper and renewable nitrogenous materials such as brewer's yeast (BY). In this study, brewer's spent grain (BSG) hydrolysate was used for L‐(+)‐LA fermentation by Lactobacillus rhamnosus ATCC 7469. The effect of pH control during the fermentation and the addition of various BY contents (5–50 g/L) in BSG hydrolysate on fermentation parameters was evaluated. BY addition significantly increased free amino nitrogen (FAN) concentration (by 25.2% at 5 g/L to 616% at 50 g/L). A strong positive correlation between FAN concentration in the hydrolysate and concentration of L‐(+)‐LA produced was observed (correlation coefficient of 0.913). A high cell viability of L. rhamnosus ATCC 7469 (1.95–3.32 × 10⁹ CFU/mL at the end of fermentation) was achieved in all fermentations with the addition of brewer's yeast. The addition of BY increased L‐(+)‐lactic acid yield and volumetric productivity up to 8.4% (5 g/L) and 48.3% (50 g/L). The highest L‐(+)‐LA yield (89%) and volumetric productivity (0.89 g/L h^?1) were achieved in fermentation of BSG hydrolysate with 50 g/L of BY. © 2019 The Institute of Brewing & Distilling     

适于生产生物柴油的产油酵母菌的筛选

该文从土壤中筛选出10株产油脂的酵母菌,经摇床培养复筛确定其中2株优良产油酵母菌JM-B、JM-D。通过对2株菌生理生化特性的试验,进一步对其发酵性能进行研究并对酵母菌株油脂脂肪酸组成进行测定。菌株JM-D油脂脂肪酸组成与植物油相似,适合用于发酵生产生物柴油,是今后发酵生产生物柴油的优良菌株。     

传统法酿造糯米酒中酵母菌的筛选及发酵特性研究

从云南传统糯米酒中分离得到16株酵母菌,通过产气性能、TTC平板显色、产酯实验的初筛方法,筛选出4株酵母菌进行复筛,再通过耐温实验、耐酒精实验、耐酸实验、发酵力实验,最终筛选出酵母菌Y1和Y2。Y1和Y2菌是理想的米酒酵母菌种,且酵母菌Y2产酯能力较强,用在米酒生产中可增加酯香味。     

小麦面筋蛋白水解物对酿酒酵母增殖和发酵性能的影响

研究了小麦面筋蛋白水解物对酿酒酵母增殖和发酵性能的影响,结果表明,不同水解度的小麦面筋蛋白水解物对酿酒酵母的促增殖和发酵效果不同,其中水解度为13.96%的水解物具有最强的促酵母增殖和发酵效果,该水解物可使稳定期酵母生物量提高37.0%,表观发酵度提高8.8%,乙醇产量提高6.4%,氨基氮利用率提高13.0%,同时发酵时间缩短14.3%。