Author: Wang, Li
Title: Feasibility analysis of fermentative lactic acid production from waste-derived crude glycerol
Degree: M.Sc.
Year: 2017
Subject: Hong Kong Polytechnic University -- Dissertations
Lactic acid -- Biotechnology
Glycerin -- Industrial applications
Department: Faculty of Construction and Environment
Pages: 100 pages : color illustrations
Language: English
Abstract: Glycerol is considered as an ideal carbon source for lactic acid fermentation, which has received attractive interest especially in the development of poly-lactic acid. In order to improve the industrial lactic acid production, a fermentation process using crude glycerol as carbon source and Lactobacillus species was investigated. E. faecalis QU 11 could convert glycerol to lactic acid with a high yield. Two essential parameters, pH value and fermentation temperature, were optimized with pure glycerol (30 g/L). The results indicated that pH value of 6.5 and fermentation temperature of 30 °C were optimal conditions that gave the best lactic acid yield (>98.5%). Then, under the same optimal conditions, the effect of substrate concentration on fermentation was investigated using crude glycerol (70 wt.%) as the substrate, a crude glycerol concentration of 30 g/L exhibited the optimum performance with a high lactic acid yield (0.743 g/g) and total carbon yield (0.997 C-mol/C-mol). Furthermore, the industrial process of lactic acid production from crude glycerol was designed and simulated by Edraw Max and Aspen Plus. A crude glycerol stream (30 g/L) was obtained during the glycerol purification process, and lactic acid was produced with a high yield of 0.751 g/g during the fermentation process. After that, a lactic acid product stream was further distillated. As a result, lactic acid with 99.92 wt.% was obtained. At the same time, economic analysis in different locations was carried out, the results indicated that the process was potentially profitable. In conclusions, the system of fermentation from crude glycerol to lactic acid was successfully established. This system could be a potential treatment for crude glycerol surplus, and provide a stepping stone to enhance the lactic acid production in industrial processes.
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