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.     

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.     

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.     

The selection and modification of brewer's yeast strains

In order to achieve a beer of high quality, the yeast culture must be effective in removing the desired nutrients from the growth medium (i.e. the wort), it must impart the required flavour to the beer and finally, the micro-organisms themselves must be effectively removed from the fermented wort after they have fulfilled their metabolic role. Brewer's wort contains the sugars sucrose, fructose, glucose, maltose and maltotriose, together with dextrin material. In the normal situation, brewer's yeast strains are incapable of fermenting the dextrin material; however, yeast strains capable of fermenting at least a part of this dextrin material and producing a palatable beer are now available.One of the important factors known to affect the fermentation rate is the intracellular yeast glycogen concentration which has been found to be influenced by storage conditions. The glycogen level at pitching significantly affects the fermentation rate of the yeast culture.     

Preparation of spent brewer's yeast β-glucans for potential applications in the food industry

A preparation of β‐glucan, obtained from spent brewer's yeast, was evaluated for potential food applications. This material was autolysed and the cell walls that were obtained were homogenized, extracted firstly with alkali, then with acid, and then spray dried. Effects of the homogenization on the chemical composition, rheological properties and functional properties of β‐glucan were investigated. Homogenized cell walls exhibited higher β‐glucan content and apparent viscosity than those which had not been homogenized because of fragmentation of the cell walls. When compared with commercial β‐glucan from baker's yeast, it was found that the β‐glucan obtained from this study had higher apparent viscosity, water‐holding capacity and emulsion stabilizing capacity, but very similar oil‐binding capacity. These findings suggest that β‐glucan obtained from brewer's yeast can be used in food products as a thickening, water‐holding, or oil‐binding agent and emulsifying stabilizer.     

维生素B1、B2含量测定方法比较

目的:比较维生素B1、B2含量测定方法。方法:采用紫外分光光度法中三种不同方法测定维生素B1、B2含量。结果:1、按E值测标示量维生素B1:98.3±2.51,维生素B2:94.8±0.308,复合维生素B片中维生素B1:102.1±1.70,维生素B1平均回收率为100.4%,RSD为2.13%(n=6),维生素B2平均回收率为94.9%,RSD为6.5%(n=6)。2、标准曲线法维生素B1、B2浓度分别在3～18、1～8μg/ml范围内,均呈良好线性关系,标示量分别为:102.9±0.661,98.4±0.152。3、双波长法测维生素B1标示量:94.2±1.97。结论:三种方法用于维生素B1、B2含量测定,操作简便、快速、准确,精密度好。     

Fumonisins B1 and B2 in Brazilian corn-based food products

Eighty-one samples of corn products were acquired from markets and supermarkets in the city of Campinas, SP, Brazil, and were analysed for fumonsins B₁ and B₂ (FB₁ and FB₂). Forty samples (49%) were positive for FB₁     

Study of fumonisins B1 and B2 contamination of baby food

Fumonisins content were studied in the baby foods, grits and flour by HPLC. FB1 +FB2 were found in 95% of 129 samples of grits and flour in quantities from 30 to 4350 microg/kg (mean: 580 microg/kg). Fumonisins were found in baby food in 52% of snacks in the range from 10 to 720 microg/kg (mean: 35 microg/kg). Processed cereal-based and cereal and dairy-based food contained FB1+FB2 in 39% of cases in the amount from 10 to 9200 microg/kg (mean: 244 microg/kg). Fumonisins were not found in canned baby food on the cereal-based with meat, fish or fruit products.     

Vitamin B1 and B2, dietary fiber and minerals content of Cruciferae sprouts

The contents in selected Cruciferae seeds and ready-to-eat sprouts of thiamine (B₁) and riboflavin (B₂) were determined by HPLC methodology. The content of soluble and insoluble fractions of dietary fiber was determined by the enzymatic method. In addition, the calcium, magnesium, zinc, cooper, ferrum and manganese concentrations were determined by atomic absorption spectrometry and after that the correlation between some mineral content and the ability of seeds and sprouts phosphate buffered saline extracts to scavenge the superoxide anion radicals in vitro was investigated. The small radish, radish, rapeseeds and white mustard seeds contained vitamin B₁ in the range from 0.41 up to 0.70 mg/100 g d.m., however its amount found in the ready-to-eat sprouts were lower by 46, 39, 42 and 47%, respectively. In contrast, the content of vitamin B₂ in the ready-to-eat sprouts showed approximately three-fold higher content when compared to its range found in the seeds (0.096 mg/100 g d.m up to 0.138 mg/100 g d.m.). The total dietary fiber content in ready-to-eat sprouts, including the soluble and insoluble forms, was 20% higher when compared to the seeds and the proportion of insoluble to soluble fiber was about two-fold higher in radish sprouts, four-fold higher in rapeseed sprouts, and six and nine-fold higher in small radish and white mustard sprouts, respectively. The sprouts contained higher amounts of Ca, Mg, Cu and Zn approximately by 12, 14, 25 and 45%, respectively, when compared to the seeds. The similar beneficial changes were noted for Cu and Zn. Their amount noted in sprouts was higher by average of 25% for Cu and by 45% for Zn. No changes in Mn and Fe levels were found between seeds and sprouts. One exception was only made to Fe content in the white mustard sprouts in which the Fe amount was lower than that found in the seeds. The SOD-like activities of the seed extracts were positively correlated only with the manganese level (r=0.94), however, this correlation was not found in ready-to-eat sprouts. No other correlations were found between SOD-like activity and microelements contents in the seeds and sprouts.     

Over-expression of GSH1 gene and disruption of PEP4 gene in self-cloning industrial brewer's yeast

Foam stability is often influenced by proteinase A, and flavor stability is often affected by oxidation during beer storage. In this study, PEP4, the gene coding for proteinase A, was disrupted in industrial brewing yeast. In the meantime, one copy of GSH1 gene increased in the same strain. GSH1 is responsible for gamma-glutamylcysteine synthetase, a rate-limiting enzyme for synthesis of glutathione which is one kind of important antioxidant and beneficial to beer flavor stability. In order to improve the brewer's yeast, plasmid pYPEP, pPC and pPCG1 were firstly constructed, which were recombined plasmids with PEP4 gene, PEP4's disruption and PEP4's disruption+GSH1 gene respectively. These plasmids were verified to be correct by restriction enzymes' assay. By digesting pPCG1 with AatII and PstI, the DNA fragment for homologous recombination was obtained carrying PEP4 sequence in the flank and GSH1 gene internal to the fragment. Since self-cloning technique was applied in the study and the modified genes were from industrial brewing yeast itself, the improved strains, self-cloning strains, were safe to public. The genetic stability of the improved strains was 100%. The results of PCR analysis of genome DNA showed that coding sequence of PEP4 gene had been deleted and GSH1 gene had been inserted into the locus of PEP4 gene in self-cloning strains. The fermentation ability of self-cloning strain, SZ-1, was similar to that of the host. Proteinase A could not be detected in beer brewed with SZ-1, and GSH content in the beer increased 35% compared to that of the host, Z-1.     

Colony-blot assay with anti-p60 antibodies as a method for quick identification of Listeria in food

The present study evaluated the ability to isolate Listeria from foods, using shortened procedure of sample enrichment followed by immunomagnetic separation or filtration methods, and serological identification of isolated bacteria by colony-blot and Western blot methods with anti-p60 antibodies. By these rapid methods, identification of Listeria was achieved in much shorter time (40-48 h) than with standard cultivation and biochemical identification procedures. The rapid methods used are easy to perform and, what is most important, their specificity is very high and fulfills the expectations. The possibility to select Listeria colonies growing on non-selective media by blotting with anti-p60 antiserum seems to be particularly valuable in examination of food samples containing/not too many Listeria (1-10 CFU/25 g). However, the blot method using anti-PepD mAb specific to unique region of L. monocytogenes p60 is necessary to distinguish L. monocytogenes from other Listeria species.     

产维生素B6乳酸菌的筛选及其鉴定

以源自内蒙古呼和浩特市婴儿粪便选出的10株乳酸杆菌为试验材料,通过微生物分析方法,筛选乳酸菌合成维生素B6能力较强的菌株并对其进行初步鉴定.结果表明,有4株菌株B25、B72、B76和N59-1合成维生素B6的能力较高,其中菌株N59-1合成维生素B6的量可高达32.62 g/100 L,菌株N59-1经鉴定为植物乳杆菌.     

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.     

啤酒糟中细菌的分离鉴定及其在啤酒糟发酵中的应用

该研究采用传统培养分离法从啤酒糟中分离细菌,通过形态观察及分子生物学技术对其进行菌种鉴定,选择其中3株细菌发酵啤酒糟,并与常规发酵真菌黑曲霉（Aspergillus niger）和出芽短梗霉（Aureobasidium pullulans）对比,以期获得对啤酒糟降解效果较好的细菌。结果表明,从啤酒糟中共分离得到6株细菌（编号为B1～B6）,经鉴定,分别为蜡样芽孢杆菌（Bacillus cereus）、梭状菌属（Clostridium sp.）、解淀粉芽孢杆菌（Bacillus amyloliquefaciens）、贝莱斯芽孢杆菌（Bacillus velezensis）、暹罗芽孢杆菌（Bacillus siamensis）、枯草芽孢杆菌（Bacillus subtilis）。其中解淀粉芽孢杆菌B3对啤酒糟的降解效果最好,且优于常规真菌,其发酵啤酒糟的蛋白质、总还原糖、阿魏酰低聚糖含量、木聚糖酶酶活、羧甲基纤维素酶酶活均最高,分别为25.26%、3.92%、10.01μmol/L、803.59 U及38.16 U。     

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%。     

Antimicrobial Properties of Vitamin B2

Riboflavin or B2, isolated from a wide variety of animals and plant products is an important vitamin commonly found in the diets of various cultures. This vitamin has been generally known to impart antimicrobial properties when exposed to ultra-violet A irradiation. In the current work, we investigated the possibility of preventing or reducing pathogenic infections using both ultra-violet A assisted and stand-alone riboflavin solutions on selected strains of bacteria. The antimicrobial properties of riboflavin were determined by the effective inhibition of the growth of pathogens through the disc diffusion method. Zones of inhibition studies indicated that riboflavin on its own was found to be quite effective and was able to inhibit the pathogens when diffused at a concentration of 50.0 µL. Stand-alone riboflavin solution successfully inhibited Staphylococcus aureus, Enterococcus faecalis, Salmonella typhi, and Pseudomonas aeruginosa with an inhibition range of (18.7 ± 0.6) mm; (17.7 ± 0.6) mm; (17.3 ± 0.6) mm, and (15.7 ± 0.6) mm, respectively. Intermediate zones of inhibition were observed for Escherichia coli and Candida albicans with a range of (11.7 ± 0.6) mm and (11.7 ± 0.6) mm, respectively. Klebsiella pneumoniae was the only resistant pathogen at (7.7 ± 0.6) mm for the riboflavin concentration used in this work. These results may indicate the exciting prospects of the applications of riboflavin as a complementary approach toward inactivation of pathogenic infections.