发酵过程酵母对麦汁糖的吸收和代谢

麦汁中含有五种可发酵性糖葡萄糖、果糖、蔗糖、麦芽糖和麦芽三糖.在大多数麦汁中,麦芽糖的浓度最高,其次是麦芽三糖和葡萄糖.酵母对以上糖的吸收按一定顺序,葡萄糖抑制了麦芽三糖的吸收,酵母吸收葡萄糖不需要消耗其代谢的能量,而对麦芽糖和麦芽三糖的吸收需要能量(活性传递).各种糖的浓度和它们相关的比例会影响到酵母对总体麦汁的发酵速率和程度.Ale啤酒酵母菌株和Lager酵母菌株对麦汁糖的吸收各有不同的特性.例如,与Lager酵母菌株相比,Ale啤酒酵母菌株很少能利用麦芽三糖.此外,麦汁中葡萄糖和麦芽三糖的浓度会影响到啤酒的风味.特别是,用提高了葡萄糖浓度的麦汁酿造的啤酒其所含的酯浓度会升高(特别是乙酸乙酯和乙酸异戊酯).而用含高浓度麦芽糖的麦汁所酿造的啤酒,其酯的浓度大大减少了.高浓酿造(＞16°P)容易发生此现象.     

利用植物乳杆菌进行啤酒生物酸化的初步研究

从长期发酵的啤酒中分离到1株乳杆菌，经鉴定为植物乳杆菌。对该植物乳杆菌的发酵产酸特性进行了初步研究，并将其应用到麦汁糖化中，利用生物酸化技术对麦芽汁进行调酸，经实验室微型啤酒糖化发酵设备生产，可得到质量优良的绿色啤酒。     

酿酒酵母麦芽汁糖代谢与啤酒发酵度研究

葡萄糖、果糖、蔗糖、麦芽糖和麦芽三糖是麦芽汁中的主要可发酵糖分.测试31株果实来源酿酒酵母菌株和工业菌株对这些糖分的代谢能力,分析其对啤酒发酵度的影响.试验结果表明,所有供试菌株都能快速代谢葡萄糖、果糖和蔗糖,都不能代谢麦芽三糖,而菌株同化和发酵麦芽糖的能力存在明显差异,差异系数分别为39.4%和33.9%;菌株的麦芽糖同化和发酵能力与真正发酵度存在强相关性,相关系数分别为0.84和0.80;果实来源菌株的总体麦芽糖同化、发酵能力及真正发酵度显著低于工业菌株(P＜0.01).选用工业菌种过程进行麦芽糖代谢鉴定是快速筛选高发酵度菌株的有效途径.     

低产乙酸啤酒酵母菌株A12的选育及中试

以啤酒酿造生产菌株啤酒酵母JM-36为出发菌株,用甲基磺酸乙酯(EMS)诱变,用含浅蓝菌素的麦芽汁琼脂平板分离抗浅蓝菌素的突变株,在低温下发酵,以发酵液的乙酸、双乙酰、乙醛、高级醇、发酵度和凝聚性为筛选指标,得到1株发酵特性优良的菌株A12。以13°BX麦芽汁为培养基,用100L发酵罐在10℃下发酵14d,菌株A12发酵液的发酵度为68.2%,乙酸、双乙酰、乙醛和高级醇的含量分别为62.3mg/L、0.081mg/L、5.321mg/L和76.43mg/L。菌株A12的主要发酵特性优良且稳定,啤酒口感良好。     

黑曲霉(Aspergilus niger)F_(27)固体曲提高啤酒糖化利用率及对啤酒质量影响的研究

黑曲霉Ｆ２７是华中农业大学生科院发酵工程室选育的一株能产较高的β—葡聚糖酶及酸性蛋白酶的菌株。本研究利用黑曲霉Ｆ２７固体曲作为复合酶制剂用于啤酒糖化，从而提高原料糖化利用率，改善麦汁组成，提高啤酒质量。结果表明，以二级麦芽为原料，利用该固体曲，原料利用率提高５．１４％。１０°Ｂｘ麦汁的α－氨基氮从１６３ｍｇ／Ｌ提高到２０ｍｇ／Ｌ，还原糖从７．６ｇ／１００ｍｌ提高到８．１ｇ／１００ｍｌ，麦汁发酵情况正常，成品酒经农业部食品检验测试中心分析及国家和湖北省评酒委员品评，其理化指标全部符合有关国家标准，风味上与正常工艺生产的啤酒无差异     

100%大麦啤酒酿造过程中老化Strecker醛的研究

分别采用上面发酵工艺与下面发酵工艺进行100%大麦啤酒及100%麦芽啤酒的酿制,并对其麦汁的氨基酸含量、老化Strecker醛、自由基以及新鲜啤酒中老化Strecker醛的含量等进行了对比分析。研究发现,就麦汁而言,100%大麦麦汁中老化Strecker醛的含量都明显低于100%麦芽麦汁;同样的麦汁,上面发酵方式还原Strecker醛的能力明显优于下面发酵方式。就啤酒而言,经酵母还原后,新鲜啤酒中的老化Strecker醛含量较麦汁含量低,且100%大麦啤酒中老化Strecker醛的含量低于100%麦芽啤酒中的含量。100%麦芽麦汁的自由基含量是100%大麦麦汁的近3倍。这都预示着100%大麦啤酒的风味稳定性（新鲜度）明显好于100%麦芽啤酒。     

高浓度双乙酰定向驯化获得优良啤酒酵母菌株的研究

在双乙酰浓度为1mg/mL的12°Bx麦芽汁中进行高浓度定向驯化,经涂布抗双乙酰固体选择培养基,从啤酒酿造生产菌株啤酒酵母(Saccharomycessp.)A中富集筛选分离得到一株双乙酰还原速度优于亲株A的新菌株TA4。以12°Bx麦芽汁为培养基用内装300mL麦芽汁的500mL三角瓶10℃下发酵,发酵8d后发酵液双乙酰含量比亲株降低了36.31%,发酵度提高4.5%,且该菌株的絮凝性、发酵速率等特性仍保持了亲株A的优良性状。     

发泡酒酿造用贫氮酵母性质的研究

研究了贫氮酵母在发酵过程中麦汁各组成成分的利用情况及其生理特性，研究发现，贫氮酵母在贫氮麦汁中能利用少部分的脯氨酸和相当部分的麦芽三糖，发酵后的啤酒中总含氮量符合淡爽啤酒的要求；它是一株中等凝聚性的酵母，具有一定的实际应用价值。     

紫外诱变选育出芽短梗霉高产普鲁兰糖白化突变菌株

为了发酵获得无色素普鲁兰糖,对菌株Aureobasidium pullulan NG进行紫外诱变,成功获得一株高产普鲁兰糖的白化突变株UVMU3-1。将突变菌株与野生菌株比较发现,其菌体生长能力和分化能力未发生显著改变。突变菌株产出的多糖经红外光谱鉴定为普鲁兰糖,罐发酵实验表明突变菌株产糖能力强于野生菌株。在未经培养基和培养条件优化的情况下,罐发酵的糖转化率可以达到52.78%。突变株UVMU3-1可作为工业发酵普鲁兰糖的潜力菌株。     

黑曲霉（Aspergillus niger）F27固体曲提高啤酒糖化利用率及对啤酒质量影响

黑曲霉Ｆ２７是华中农业大学生科院发酵工程室选育一株有产较高的β－葡聚糖酶及酸性蛋白酶的菌株，本研究利用黑曲霉Ｆ２７固体曲作为复合酶制剂用于啤酒糖化，从而提高原料糖化利用率，改善麦汁组成，提高啤酒质量。结果表明，以二级麦芽为原料，利用该固体曲，原料利用率提高５．１４％，１０＾Ｂｘ麦汁的α－氨基氮从１６３ｍｇ／Ｌ提高到２０ｍｇ／Ｌ，还原糖从７．６ｇ／１００ｍｌ提高到８．１ｇ／１００ｍｌ，麦汁发酵情况正     

Mutagenizing brewing yeast strain for improving fermentation property of beer

A brewing yeast mutant with perfect sugar fermentation capacity was isolated by mutagenizing the Saccharomyces pastorianus transformant, which carries an integrated glucoamylase gene and has one copy of non-functional alpha-acetolactate synthase gene. The mutant was able to utilize maltotriose efficiently, and the maltotriose fermentability in YNB-2% maltotriose medium increased from 32.4% to 72.0% after 5 d in shaking culture. The wort fermentation test confirmed that the sugar fermentation property of the mutant was greatly improved, while its brewing performances were analogous to that of the wild-type strain and the characteristic trait of shortened beer maturation period was retained. Therefore, we believe that the brewing yeast mutant would benefit the beer industry and would be useful for low caloric beer production.     

啤酒酵母乙醛代谢关键酶相关性研究

乙醛是啤酒中的主要风味物质,其代谢主要来自酵母细胞。酵母中乙醇脱氢酶及乙醛脱氢酶是乙醛代谢的关键酶,对乙醛变化起着重要作用。跟踪啤酒酵母发酵过程中相对酶活力及乙醛变化,发现两种乙醇脱氢酶和乙醛脱氢酶的相对酶活力与发酵过程乙醛含量变化具有一定相关性。同时对低产乙醛啤酒酿酒酵母kb2-4与出发菌株啤酒酵母kb进行发酵试验,跟踪检测相对酶活力及乙醛含量,其乙醇脱氢酶Ⅰ和乙醇脱氢酶Ⅱ及乙醛脱氢酶相对酶活力均高于出发菌株,平均增幅分别为15.5%,11.6%和5%。3种酶活性的变化协同作用可以使乙醛含量降幅最大为33.8%。     

“珠研”2~＃菌株缩短发酵周期的生产性试验研究（初报）

经诱变、筛选处理的“珠研”２~＃菌株经小试、中试证明其啤酒发酵性能比原引进的菌株有较大的优越性。为验证此菌株对麦汁及扩大生产的适应性，我们对此菌株进行生产性扩大试验。实践证明，“珠研”２~＃菌株对麦汁及扩大生产适应性较强。该菌株具有发酵温度高、降糖快、双乙酰还原能力强、酵母凝集性好、发酵周期短、生产的啤酒质量优越等优点。取得与小试、中试基本一致的结果。我们认为“珠研”２~＃菌株啤酒快速发酵新工艺，可望有良好的推广应用前景。     

抗老化啤酒酵母的选育

以无锡轻工大学生物工程学院保藏的一株啤酒酵母为出发菌株，经紫外线诱变及蛋氨酸连续驯养后，选育得到一株抗老化性能较为优良的菌株Ｍ４．在１ｍ３发酵罐中的中试结果表明，与出发菌株相比，其羰基化合物（ＴＢＡ）含量降低１９．１％，谷胱甘肽（ＧＳＨ）含量增加２９．６％．在不改变其它生产条件的情况下，啤酒风味稳定性提高９２％，工业应用前景良好。     

Construction of recombinant industrial brewer’s yeast with lower diacetyl production and proteinase A activity

The characteristic buttery taste of diacetyl has long been a major problem in the brewing industry, and the foam stability of unpasteurized beer is often influenced by proteinase A (PrA), which is encoded by PEP4 and released from yeast cells into beer during brewing. A recombinant industrial brewer’s yeast strain that reduces the diacetyl content of beer and improves foam stability was constructed. We constructed a PGK1p-ILV5-PGK1t expression cassette, which was introduced into one of the PEP4 alleles via PCR-mediated homologous recombination. Then, the second PEP4 allele was disrupted using the Cre-loxP recombination system, and the recombinant strain was designated as S-CSIK12. The results show that the diacetyl production of S-CSIK12 is always lower than that of the host strain at all stages of beer fermentation. In addition, brewing with S-CSIK12 reduced the PrA activity of the final beer by 44 % compared with that using the wild-type strain. The head retention of the beer brewed with S-CSIK12 (260 ± 2 s) was better than that of the host strain S-6 (212 ± 3 s). Considering that more PrA is released from yeast cells during the final stage of main fermentation and that the timing of yeast cropping is determined by diacetyl reduction, brewing with strains that have low diacetyl production also reduced the PrA activity of the beer and improved its head retention. The present study provides reference for the brewing industry as well as research on the diacetyl reduction and foam stability of beer.     

Attachment of MAL32-encoded maltase on the outside of yeast cells improves maltotriose utilization

The fermentation of maltotriose, the second most abundant fermentable sugar in wort, is often incomplete during high-gravity brewing. Poor maltotriose consumption is due to environmental stress conditions during high-gravity fermentation and especially to a low uptake of this sugar by some industrial strains. In this study we investigated whether the use of strains with an alpha-glucosidase attached to the outside of the cell might be a possible way to reduce residual maltotriose. To this end, the N-terminal leader sequence of Kre1 and the carboxy-terminal anchoring domain of either Cwp2 or Flo1 were used to target maltase encoded by MAL32 to the cell surface. We showed that Mal32 displayed on the cell surface of Saccharomyces cerevisiae laboratory strains was capable of hydrolysis of alpha-1,4-linkages, and that it increased the ability of a strain lacking a functional maltose permease to grow on maltotriose. Moreover, the enzyme was also expressed and found to be active in an industrial strain. These data show that expressing a suitable maltase on the cell surface might provide a means of modifying yeast for more complete maltotriose utilization in brewing and other fermentation applications.     

果酿啤酒的酿造工艺和品质研究进展

果酿啤酒的品质受众多因素影响,特别是水果特性差异和产品质量标准缺失使得果酿啤酒的酿造工艺存在较大差别,产品质量难以稳定。为进一步提升果酿啤酒品质,该文对近年来果酿啤酒的研究现状进行综述,探讨水果榨汁处理、灭菌方式,发酵过程中原麦汁浓度、主发酵温度、果汁添加量及添加阶段、酵母菌种选择等因素对果酿啤酒品质的影响,分析果酿啤酒的风味成分及风味劣变、活性成分及抗氧化活性,并对果酿啤酒的发展趋势及品质提升进行展望,以期实现不同果酿啤酒的精准调控,为实际生产中果酿啤酒的酿造提供借鉴。     

安琪啤酒活性干酵母在啤酒生产中的应用

安琪啤酒活性干酵母是湖北安琪酵母股份有限公司运用现代生物高新技术开发出的新一代啤酒酵母菌种，具有耐高温、耐乙醇、耐高渗透压等特点。经多次实验证明，此菌种可在不同的发酵起始温度下发酵生产啤酒，便于生产工艺控制，弥补了传统啤酒生产工艺的不足，提高了生产效率，降低了生产成本。     

Elaboration of the Technology for the Production of Bierbrand in a Pilot Plant

Bierbrand is an alcoholic beverage that is made by the distillation of beer prepared especially for this purpose. The goal of our work was to elaborate the technology to produce bierbrand in a pilot plant. It included optimization of the brewing and fermentation of the beer that serves as the basic material of distillation, and the optimization of the distillation process itself. Raw materials were selected to achieve a beer rich in aroma, and with the highest possible alcohol and original extract content. Distillate of beer fermented with a top fermenting yeast strain provided the best product. Storage of the distillate for 3 weeks improved its quality significantly.