利用纳滤膜技术分离秸秆发酵液中糖和乳酸的研究

Investigation on separation of residual sugar and lactic acid from straw fermentation broth by nanofiltration technology

本文旨在研究以秸秆类生物质为原料的L-乳酸发酵液中L-乳酸与残糖的纳滤分离工艺和特性.基于特有的高浓度L-乳酸发酵液的多组分体系,考察了pH、跨膜压差、温度和离子强度对L-乳酸与残糖纳滤分离的影响,成功开发了糖/酸三级纳滤分离工艺.在最优纳滤条件(pH=2.00、压力2 MPa、温度25℃)下,乳酸纯度(质量分数)由92.4%提升至99.7%,每级纳滤的乳酸收率均高于80.0%,同时达到了理想的脱色效果.此外,在机理方面,将CFSK模型(Combined Film-theory SKK model)的内、外插值结果与实验数据进行比对,证实了CFSK模型用于描述秸秆发酵液体系中糖/酸纳滤分离的适用性和准确性.

This study aims to investigate the nanofiltration membrane separation technology to separate the residual sugars and the L-lactic acid from straw biomass fermentation broth.Based on the unique multicomponent fermentation broth system with high concentration of L-lactic acid,the effects of pH,transmembrane pressure,temperature and ionic strength on the separation of residual sugars and L-lactic acid were investigated.Based on the optimal nanofiltration conditions(pH=2.00,2 MPa,25℃),a threestage nanofiltration separation process was designed to perform nanofiltration separation on the actual fermentation broth.The purity of L-lactic acid was increased from 92.4% to 99.7%.The yield of L-lactic acid was higher than 80.0% in each stage,and the ideal effect of decolorization were achieved simultaneously.In terms of mechanism,the applicability and accuracy of CFSK model in describing nanofiltration separation of lactic acid and residual sugar in the straw fermentation broth system were established for the first time by comparing the internal and external interpolation results of the model with the experimental data.