【作者】 徐玲；

【导师】 周广田；

【作者基本信息】 山东轻工业学院 ， 发酵工程， 2008， 硕士

【摘要】 废酵母是啤酒生产过程中的副产物,约占啤酒产量的2%～3%。在当前资源短缺,环境污染严重的现状下,对废酵母进行开发利用,对减轻废酵母的环境污染,增加啤酒行业效益有重要的意义。目前,酵母的加工方法主要是将酵母泥直接烘干,或用压滤机对酵母进行分离,然后对分离出的酵母进行干燥,生产商品酵母粉。但在酵母的干燥过程中会产生大量的废蒸汽,其中含有4.5%左右的酒精,排放到空气中,既污染了环境,又造成了资源浪费,尚未引起企业的重视。针对这种现状,本课题的目的就是要回收利用这部分酒精资源,并以回收的酒精为原料采用醋酸液态深层发酵与萃取-蒸馏工艺或共沸精馏工艺相结合生产高酸醋,此产品可用于食品与化妆品行业,具有广泛的应用前景。本课题的内容和结果如下:1.列管式换热器冷凝、吸收塔吸收回收酒精。采用适当型号的列管式换热器和吸收塔回收酒精,回收率达到90%左右。回收的酒精溶液经连续蒸馏塔蒸馏去杂,得到的酒精经检测,符合食用酒精标准,可作为醋酸发酵产酸的原料。2.以酒精为原料添加废酵母自溶液发酵产酸。在以酒精为原料发酵产酸的过程中,为了维持正常的醋酸发酵需添加少量含碳、氮源的营养液。本课题通过实验确定了废酵母自溶液的最佳制备工艺及以酒精为原料发酵产酸的工艺配方,探索了采用廉价的废酵母自溶液作为有机氮源进行醋酸发酵的可行性。结果表明,以废酵母自溶液作为醋酸发酵的有机氮源是可行的。当以自溶液为有机氮源替代酵母浸粉时,醋酸菌浓度的提高超过54%,醋酸含量的提高超过10%。自溶液的最佳制备工艺为:加水量200%,初始pH值7.0,自溶温度50℃,时间48h,食盐优化用量3%。以酒精为原料发酵产酸的最佳配方为:酒精浓度5%,酵母液添加量13%,菌种接种量12%。3.萃取-蒸馏或共沸精馏生产高酸醋。结果表明,通过萃取-蒸馏或共沸精馏可以生产出25%左右的高酸醋,达到了课题的目标要求。萃取-蒸馏时,采用乙酸乙酯作为萃取剂,萃取时间为20min,最佳溶剂比为1.0,三级错流萃取后,水相中的醋酸浓度为0.79g/100mL,达到目标要求。共沸精馏时,采用乙酸丁酯作为共沸剂;随着共沸剂含量的增加,塔釜醋酸浓度逐渐增加,但随着共沸剂含量的进一步增加,醋酸浓度下降,而塔顶醋酸浓度均控制在一个比较小的范围内;水与共沸剂的配比固定时,随着样品醋酸浓度的增加,塔釜醋酸浓度增加;共沸剂的平均回收率为95.33%,损失较少,基本可以回收重复利用。更多还原

【Abstract】 The waste yeast is the by-product during the brewing process, accounting for approximately 2%～3% of the total beer output. Under the status of resources shortage and serious environment pollution, it is necessary to develop and explore the waste yeast to reduce pollution and increase benefits of beer industry. Now, the yeast is mainly dried directly, or filtered to be separated and then the separated yeast is dried. However, a lot of waste steam will produce in the process of yeast drying, which contains 4.5% alcohol. If the waste steam releases into the air, not only the environment is polluted, but also the resources are wasted. Enterprises have not yet aroused the attention.In view of this situation, the purpose of this paper is to utilize the alcohol resources and produce high sour vinegar using the alcohol as material and using the submerged fermentation and extraction-distillation process, or azeotropic distillation process as method. This product can be used in food and cosmetic industries, which has a broad application prospect. The contents and results are as follows:1. Alcohol recovery using tubular heat exchanger and packed absorption towerThe recovery ratio was about 90% adopting appropriate models of tubular heat exchanger and packed absorption tower. The recoverable alcohol solution was distilled to remove impurities using continuous distillation column. Through detecting, the distilled alcohol accorded with the edible alcohol standard. And it was feasible to produce acetic acid using the alcohol.2. Acetic fermentation using alcohol as material adding yeast autolysis solutionIn the process of acetic fermentation using alcohol as material, a small amount of nutrient solution containing carbon and nitrogen was added in order to maintain normal acetic fermentation. The optimal preparation technology of yeast autolysis solution and the formulation of acetic fermentation using alcohol as material were established through experiments. A new kind of organic nitrogen, yeast autolysis solution, was attempted to be used during the process of acetic acid fermentation. The results indicated that it was feasible to use yeast autolysis solution as organic nitrogen in the process of acetic acid fermentation. The concentration of acetic acid bacteria and acetic acid were improved more than 54% and 10%, respectively, when yeast autolysis solution was used instead of yeast extract. The optimal preparation technology of yeast autolysis solution solution was as follows: water 200%, initial pH 7.0, autolysis temperature 50℃, autolysis time 48h and NaCl 3%. The optimal formulation of acetic acid fermentation was as follows: 5% alcohol, 13% yeast autolysis solution, 12% inoculum.3. High sour vinegar production using extraction-distillation or azeotropic distillation as methodTest results indicated that 25% high sour vinegar could be produced, which achieved the objective and requirement of the subject, through extraction-distillation or zeotropic distillation. In the process of extraction-distillation, acetic ether was used as extration solvent and the optimal technology for the production of high sour vinegar was as follows: 20 minutes extraction, 1.0 proportion of solvent. The acid concentration in the water was 0.79g/100mL, which met the requirement, through three cross-flow extractions. In the process of azeotropic distillation, butyl acetate was used as azeotropic agent. With the increase of the azeotropic agent’s content, acid concentration of Still Pot gradually increased. But with a further increase of azeotropic agent’s content, the acid concentration decreased. The acid concentration of tower’s top was controlled in a relatively small area. When the ratio of water to azeotropic agent was fixed, with the increase of acid concentration of sample, acid concentration of Still Pot increased. The average recovery rate of azeotropic agent was 95.33% and the azeotropic agent could be reused.更多还原