【作者】 胡维胜；

【导师】 潘丽军；

【作者基本信息】 合肥工业大学 ， 农产品加工及贮藏工程， 2005， 硕士

【摘要】 乳酸广泛应用于化工、食品和医药等领域,市场前景广阔。但用于食品和医药行业中的乳酸不仅要求其构型为L-型,而且光学纯度高、杂质含量少、稳定性好。目前国内外主要用发酵法生产L-乳酸,其分离提取工艺复杂,产品收率低,经济效益不高。论文开展了以甘薯淀粉为碳源,采用米根霉菌株As3. 819发酵生产L-乳酸的分离纯化工艺研究。针对目前国内L-乳酸分离精制生产技术中存在的主要问题,对传统钙盐提取工艺进行了探索改进。设计提出了采用截留分子量为5000道尔顿的超滤膜去除蛋白、颗粒状活性炭和AB-8大孔吸附树脂联合脱糖脱色、乳酸钙梯度降温结晶等除杂纯化工艺,建立了纯化工艺中主要组分准确便捷的分析检测方法,考查了各个工序的关键影响因素,在此基础上选择优化出食用级L-乳酸分离精制的工艺路线和最佳操作参数。实验结果表明:使用颗粒活性炭和AB-8大孔吸附树脂进行脱糖脱色,乳酸的损失率仅为7. 8%,远低于传统工艺中采用单一粉末活性炭重复处理所造成的20-30%乳酸损失率,能去除绝大部分残糖和色素杂质;运用超滤膜技术处理发酵液,蛋白去除率可达91. 56%, L-乳酸的损失率为2%,与目前乳酸分离精制工艺中所采用的加热碱调、添加絮凝剂除蛋白工艺相比,具有明显优势;采用梯度降温和晶种诱导进行乳酸钙结晶技术,结晶率可达67. 46%,对母液回收后可进行再次结晶。经过优化组合的食用级L-乳酸分离精制工艺合理,操作简单,各工序连续性较好,L-乳酸提取率可达70%以上,经纸层析及对成品L-乳酸旋光性检测的结果表明,其L-乳酸含量为90%、光学纯度为95%,产品稳定性较好。更多还原

【Abstract】 Lactic acid and its derivatives, widely used in the chemical, food, pharmaceutical industries, are promising products. For food and pharmaceutical purposes, however, with high optical purity L- lactic with lower content of impurities are required. Currently, L- lactic acid is mainly produced by fermentation method, which suffers some difficulties such as complex separation process, poor recovery rate and low efficiency.This thesis focused on the downstream purification process of lactic acid produced by Rhizopus oryaze 3.819 from sweet potato starch. For lactic acid clarification and purification, a series of technologies were introduced, which covered ultrafiltration membrane with 5000D retention molecular weight for protein removal, particle active charcoal in combination with macroporous AB-8 resin for sugar and pigments removal , and gradual temperature decrease for calcium lactate crystallization. Firstly, fast and accurate assays related to purification process were established for the main components analysis. Secondly, the key factors in every process were further researched. Finally, the process of food-grade lactic acid and its parameters were optimized.The results were as follows: by using particle active charcoal and AB-8 macroporous adsorbent resin for color and sugar removal, the loss rate of calcium lactate in the process was only 7.8%, which was much lower than that of 20-30% in the conventional process caused by powder charcoal. In addition, most sugar and pigments were removed. For ultrafiltration technique, it had advantages in separating protein over traditional process. Its retention rate of protein and the loss rate of calcium lactate were about 91.56% and 2%, respectively. Gradual temperature decrease and crystal seeds addition were adopted for crystallization of calcium lactate, in which crystallization rate could be up to 67.4%. Furthermore, its mother liquid can be reused for crystallizing.The optimized process of food-grade lactic acid had some advantages such as lower energy consumption, simpler operation requirements and better continuity. The recovery rate of lactic acid could reach 70%. Revealed from the results of paper chromatography and optical polarity, the content of refined lactic acid was 90% with optical purity of 95%, and its stability was superior.更多还原