佛手汁酿制果醋的过程需要优先利用酵母菌将糖发酵为酒精,但佛手汁中的柠檬苦素会抑制酵母生长.为避免其对酵母酒精发酵能力的影响,作者利用佛手为原料,结合醋酸发酵的选育方式,筛选适合佛手果醋乙醇发酵的酵母菌株.从自然发酵的佛手汁中,分离得到85株酵母菌株.经过杜氏小管初筛,以产乙醇能力、起酵速度、有机酸生产能力为指标进行复筛和醋酸发酵试验,最终得到优良菌株FS-ZJQ.经18S rDNA序列鉴定该酵母菌株为酿酒酵母.其在糖度18°Bx的佛手汁中,25 ℃发酵7d可产乙醇8.49％,发酵液中萜烯类化合物、酯类化合物质量分数高,分别占挥发性风味成分的58.83％、16.44％;经醋酸发酵后,非挥发酸质量浓度可达5.06mg/mL.菌株FS-ZJQ对糖度、pH、乙醇的耐受性较好.

研究了新型啤酒稳定剂BFSA对啤酒蛋白质的吸附特性,初步探讨了BSFA吸附蛋白的作用机理.FT-IR图谱分析可知,BFSA表面含有Si-O-Si键,且含有O-H键.研究了时间、温度、蛋白质浓度对BFSA吸附的影响,发现吸附平衡时间在1h左右,BFSA吸附啤酒蛋白质量随温度的降低而升高,随着初始蛋白质浓度的升高而升高.研究了BFSA吸附啤酒蛋白质的吸附等温线、动力学和热力学模型,发现BFSA对啤酒蛋白质的吸附等温线更符合Freundlich方程;对啤酒蛋白质的吸附过程更符合准二级动力学方程;由热力学参数△G＞0说明啤酒蛋白质在BFSA表面的吸附为非自发的,ΔH＜0说明吸附过程是放热的,△S＜0说明吸附是熵减过程;活化能(E)为26.28 k J/mol表明BFSA吸附啤酒蛋白质是物理吸附;吸附过程放热为6.62 kJ/mol表明该吸附过程的主要作用力可能是范德华力、氢键和疏水作用.

Yeast cell wall plays an important role in the establishment and maintenance of cell morphology upon the cell wall stress. The cell wall of yeast consists of β-glucans, mannoproteins and chitin. The composition and structure remodel due to cell wall stress. Brewer's yeast cell wall exhibits stress response during long-term acclimation in order to adapt to environmental changes. This paper reviews the composition and structure of yeast cell wall and the molecular mechanisms of cell wall remodeling and signal pathway regulation.

Gibberellic acid (GA3) was added to three types of beer barley, and the chemical changes to GA3 during the beer brewing process were studied using HPLC. The results demonstrated that the GA3 concentration decreased throughout the malting, mashing, and boiling processes and that no GA3 was detected in the congress wort. A new substance, herein called Substance A, was detected by HPLC analysis using a C18 column; this substance exhibited retention characteristics different from GA3. The concentration of Substance A increased throughout the malting, mashing, and boiling processes. Mass spectrometry revealed that Substance A has the same molecular weight as GA3 and nuclear magnetic resonance studies determined that Substance A is a structural isomer of GA3. Practical Application This study developed a new idea to understand GA3 behavior during the brewing, which provided a practical reference for food safety in beer and other fields using GA3 as a food additive.

Objective: To simultaneously increase the thermostability and catalytic activity of barley beta-amylase. Methods: The amino acid sequences of various barley beta-amylases with different enzyme properties were aligned, two amino acid residues R115 and T387 were identified to be important for barley beta-amylase properties. R115C and T387V were then generated using site-directed and saturation mutagenesis. Results: R115C and T387V mutants increased the enzyme catalytic activity and thermostability, respectively. After combinational mutagenesis, the T-50 value and t((1/2,60C))(o) value of R115C/T387V mutant reached 59.4 degrees C and 48.8 min, which were 3.6 degrees C higher and 29.5 min longer than those of wild-type. The k(cat)/K-m value of mutant R115C/T387V were 59.82/s.mM, which were 54.7% higher than that of wild-type. The increased surface hydrophobicity and newly formed strong hydrogen bonds and salt bridges might be responsible for the enzyme thermostability improvement while the two additional hydrogen bonds formed in the active center may lead to the catalytic property enhancement. Conclusions: The mutant R115C/1-387V showed high catalytic activity and thermostability indicating great potential for application in industry. (C) 2019 Elsevier Inc. All rights reserved.

文章针对酿酒工业分析(含实验)课程教学和人才培养要求,对课程教学目标、教学内容、教学方法和考核方式进行了系统分析,提出了提高教学质量和人才培养的改革方式,以期为酿酒行业分析检测人才的培养提供参考.

采用顶空固相微萃取-气相色谱-质谱联用(solidphase microextraction-gas chromatography-mass spectrometry,SPME-GC-MS)技术与气相色谱-闻香法(gas chromatography-olfactometry,GC-O)中时间强度法和香气活度值(odor activity value,OAV)相结合的方法,探究红心火龙果果酒中特征香气物质.自制红心火龙果果酒中特征香气物质主要为己酸乙酯(OAV=276.45,下同)、乙酸异戊酯(103.54)、辛酸乙酯(50.45)、异戊醇(4.32)、乙酸乙酯(3.50)、苯乙醇(3.36);市售红心火龙果果酒样品1中主要为己酸乙酯(95.41)、乙酸异戊酯(41.97)、丁二酸二乙酯(19.00)、乙酸乙酯(12.12)、辛酸乙酯(11.67)、异戊醇(4.36);市售红心火龙果果酒样品2中主要为己酸乙酯(53.80)、丁二酸二乙酯(25.08)、乙酸异戊酯(17.64)、乙酸乙酯(16.55).该研究首次分析确定了红心火龙果果酒中的特征香气物质,明晰香气物质对果酒的贡献程度,为火龙果果酒品质的调控和提升提供理论依据.

为了评价采用酒花抗性基因horA和horC作为分子标记,快速检测和鉴定具有腐败能力的啤酒污染菌的准确性,对来自5家工厂的53株啤酒污染菌基因型和表型进行比较分析,包括M13-PCR指纹、horA/horC的PCR扩增、菌株的酒花抗性和啤酒腐败能力.M13-PCR指纹的聚类分析表明不属于同一菌种的指纹相似性一般小于70％,同菌种不同菌株之间的指纹也存在较大差异,因此53株菌株之间存在一定的个体差异.表型的比较分析表明,酒花抗性或腐败性较强的菌株,horA /horC检测结果一般为阳性,针对这一类菌株其检测准确性较高.然而,部分弱酒花抗性或无腐败能力的菌株,horA/horC检测结果也为阳性,其中无腐败能力的菌株的假阳性检出率达到了78.6％;部分弱腐败能力菌株的horA /horC检测为阴性,即假阴性率为28％.2株具有较强酒花抗性的菌株的horA/horC检测为阴性,表明可能存在新的酒花抗性机制.令人感兴趣的是,通过菌株间的比较分析表明horA/horC在L.plantarum中具有较高的保守性.以上研究结果表明,horA/horC作为单一的分子标记,难以准确地检测和鉴定所有啤酒污染菌的酒花抗性和腐败性.

1,3-1,4-β-glucanase (E.C.3.2.1.73) is an important industrial enzyme which cleave β-glucans into oligosaccharides through strictly cutting the β-1,4 glycosidic bonds in 3-O-substituted glucopyranose units. Microbial 1,3-1,4-β-glucanase belongs to retaining glycosyl hydrolases of family 16 with a jellyroll β-sandwich fold structure. The present paper reviews the industrial application and protein engineering of microbial β-glucanases in the last decades and forecasts the research prospects of microbial β-glucanases.

采用将特种麦芽的糖化麦汁稀释至固定色度值的方法,分析了不同麦芽间的颜色特征,实验结果表明部分麦芽具有明显的红色调,结合麦芽色度对该类别麦芽进行了范围限定,将之定义为红色系麦芽.同时,引入了红色强度来有效表达糖化麦汁的颜色变化,并确定了适合酿制红啤酒的糖化麦汁的颜色范围.后通过发酵试验将红色强度范围修正为0.215 ～0.330,当红啤酒出现番茄红等较为鲜亮的红色时红色强度范围为0.215～0.302.

OBJECTIVE:To improve the aroma profile of beer by using metabolic engineering to increase the availability of cytosolic NADH in lager yeast.RESULTS:To alter NADH levels in lager yeast, the native FDH1 (YOR388C) encoding NAD+-dependent formate dehydrogenase was overexpressed in the yeast strain M14, yielding strain M-FDH1. This led to a simultaneous increase of NADH availability and NADH/NAD+ ratio in the M-FDH1 strain during fermentation. At the end of the main fermentation period, ethanol production by strain M-FDH1 was decreased by 13.2%, while glycerol production was enhanced by 129.4%, compared to the parental strain respectively. The production of esters and fusel alcohols by strains M14 and M-FDH1 was similar. By contrast, strain M-FDH1 generally produced less organic acids and off-flavor components than strain M14, improving the beer aroma.CONCLUSIONS:Increased NADH availability led to rerouting of the carbon flux toward NADH-consuming pathways and accelerated the NADH-dependent reducing reactions in yeast, greatly impacting the formation of aroma compounds and improving the beer aroma.

Cider Beer是一种以苹果汁为原料,结合啤酒酿造工艺研制的发酵型特种啤酒.通过发酵实验,发酵度、乙醇体积分数等指标检测,本产品选取7号浓缩苹果汁作为原料;通过对比贫氮条件下不同酵母的生长情况和发酵实验结果,最终确定酵母C作为发酵菌株.以感官品质为考察指标,采用单因素正交实验法考察发酵温度、发酵时间和酵母接种量对感官品质的影响.结果 表明:Cider Beer的较佳发酵工艺条件为:发酵温度11℃,发酵时间7d,酵母接种量8×106个/mL,所得产品的总糖质量浓度为13.28 g/L,总酸质量浓度为6.5 g/L,乙醇体积分数为2.85％,游离氨基酸质量浓度为3.60 g/L,多酚质量浓度为1.04 g/L,色香味俱佳.

为筛选适合火龙果酒酿造的酵母菌株,从多种浆果表面分离获得200株酵母菌株,在杜氏小管发酵的基础上,进一步在火龙果汁中发酵筛选出发酵性能好并具有较好香气的菌株.结合风味物质分析及感官品评获得1株起酵速度快且果酒香气浓郁、具有火龙果典型特征香气的菌株194.通过18S rDNA序列比对,鉴定其为酿酒酵母,可用于食品发酵.

FKS作为1,3-β-葡聚糖合成酶基因家族,对维持酿酒酵母细胞壁有重要作用.为探究FKS家族基因对酿酒酵母细胞抗逆性及其合成乙醇的影响,通过同源重组的方法分别构建了FKS1、FKS2和FKS3基因的缺失菌株,并比较重组菌株和原始菌株的性能差异.结果表明,FKS1缺陷菌株细胞壁的1,3-β-葡聚糖含量低于原始菌株60％,生长性能、抗胁迫性以及合成乙醇能力都较差.FKS3缺陷菌株的生长性能和胁迫性能与原菌株相似,在发酵环境中抵抗外界环境能力和合成乙醇能力优于原始菌株.因此,FKS1基因对维持酵母细胞活性和抗逆有重要作用,而FKS3基因对抗逆有负面作用.

Acetaldehyde is synthesized by yeast during the main fermentation period of beer production, which causes an unpleasant off-flavor. Therefore, there has been extensive effort toward reducing acetaldehyde to obtain a beer product with better flavor and anti-staling ability. In this study, we discovered that acetaldehyde production in beer brewing is closely related with the intracellular NADH equivalent regulated by the citric acid cycle. However, there was no significant relationship between acetaldehyde production and amino acid metabolism. A reverse engineering strategy to increase the intracellular NADH/NAD(+) ratio reduced the final acetaldehyde production level, and vice versa. This work offers new insight into acetaldehyde metabolism and further provides efficient strategies for reducing acetaldehyde production by the regulating the intracellular NADH/NAD(+) ratio through cofactor engineering.

Serial repitching of beer brewer’s yeast plays an important role in the beer industry as an ineluctable economic factor. In this study, the viability and vitality changes, as well as strains’ anti-autolytic abilities during serial beer fermentation with typical ale and lager yeast strains, were investigated. While measuring the survival rate of yeast cells is not sufficient for evaluating and predicting the yeast fermentation capacity, physiological status determination of brewer’s yeast reflects the vitality and quality of yeast in serial beer fermentations. Accumulation of reactive oxygen species in yeast causes cell damage, leading to a decline in cell vitality and viability. Aged yeast cells, after several repitchings, can result in leakage of intracellular compounds into the fermented liquor. The lager yeast (Pilsner) examined, which harbors the partial genome from S. eubayanus, showed better robustness and higher activity than the ale yeast strain M79 examined, during serial fermentation. A holistic approach, including more indicators, should be applied in evaluating the fermentation performance of brewer’s yeast.

γ-氨基丁酸(γ-aminobutyric acid,GABA)是一种具有降血压等多种重要生理功能的天然非蛋白质氨基酸,在食品工业中已有广泛应用,但在啤酒工业领域研究较少.对本实验室研究开发的青稞红曲啤酒和市售啤酒进行对比发现,市售啤酒中GABA质量浓度范围介于40～65 mg/L之间,青稞红曲啤酒中GABA质量浓度为91.3±6.9 mg/L.通过对原料、糖化和发酵工艺的研究可知,糖化过程中GABA在糖化初期含量增加,随着糖化的进行,麦汁中GABA质量浓度逐渐平稳,青稞麦芽的比例对麦汁中GABA质量浓度有较大影响,青稞红曲的添加会增加麦汁中GABA的质量浓度;麦汁经发酵过程,GABA的损失率为10.7％.

着重探讨了添加大米辅料对啤酒中蛋白质疏水性和泡沫稳定性的影响.研究发现,大米辅料添加量从10％增加到30％,疏水性指数从118.86逐渐减少至103.87,而泡沫稳定性由62.14％增加到68.25％.通过十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(sodium dodecyl sulfate-polyacrylamide gelelectrophoresis,SDS-PAGE)分析啤酒中来源于大米的蛋白质,发现大米啤酒中蛋白质Z含量较小而且含有一定量的RAG2蛋白,从而对啤酒泡沫稳定性形成一定的影响.

The role of proteins, especially protein Z, on beer foam stability was studied. The results showed that both positive and negative proteins were enriched in beer foam. Contrary to previous results, proteins with lower surface hydrophobicity were preferred for beer foam stability. Among all proteins, protein Z was the most prevalent protein in beer foam and could be accurately measured using an enzyme linked immunosorbent assay. The quantity of protein Z was found to be positively correlated with beer foam stability. The addition of purified protein Z from barley (Hordeum vulgare) malt into the finished beer could enhance the beer foam stability. Therefore, proteins with lower surface hydrophobicity might be beneficial for beer foam stability, especially protein Z.

This study aimed to elaborate the effect of N-glycosylation and glycation of protein Z4 from barley malt and recombinant Pichia pastoris on beer foam stability. The malt protein Z4 and recombinant protein Z4 showed similar N-glycosylation patterns while recombinant protein Z4 was glycosylated at a higher degree. In the simulated mashing and boiling, malt protein Z4 and deglycosylated malt protein Z4 preferred to glycate with glucose and maltose while recombinant protein Z4 and deglycosylated recombinant protein Z4 showed preference towards fructose. The addition of protein Z4 and protein Z4-saccharide complexes in finished beer showed that the addition of glycosylated protein Z4 only slightly enhanced the beer foam stability while the addition of glycated protein Z4 and protein Z4 with both glycation and glycosylation could significantly increase the beer foam stability. Therefore, glycation instead of N-glycosylation of protein Z4 played important roles in maintaining beer foam stability.