Study On Biorefinery Processes Technology On Lactic Acid Production From Lignocellulose And Inulin Biomass

The sharp increase in manufacturing biodegradable polylactic acid (PLA) has significantly stimulated lactic acid production from low value and abundant agricultural residues materials such as inulin, corn stover, wheat straw, and rice straw. In this thesis, the biorefinery processing technology for fermentative production of lactic acid using inulin and lignocellulose biomass as the raw materials wasintensively studied.First, an interesting lactic acid bacteria strain, Pediococcus acidilacticiDQ2, was isolated from the corn stover slurry of ethanol fermentation. P. acidilactici DQ2was identified using16S DNA sequencing and microbial methods. The unique properties of P. acidilaclici DQ2, the excellent thermo-and inhibitor-tolerance, were demonstrated and carefully investigated.Then, the newly isolatedP. acidilactici DQ2strain was applied to the lactic acid fermentation using Jerusalem artichoke tubers (Jat) as the raw materials. A high inulinase activity was found in three commercially available glucoamylase enzymes. Its origin was investigated and two proteins in the commercial glucoanylases were identified as the potential enzymes showing inulinase activity. One of the commercial glucoamylases, GA-L New from Genencor, was used for Jerusalem artichoke tubers (Jat) hydrolysis and a high hydrolysis yield of fructose was obtained. The simultaneous saccharification and lactic acid fermentation (SSF) of Jat was carried out using GA-L New as the inulinase and P. acidilactici DQ2as the fermenting strain. A high lactic acid titer, yield, and productivity of111.5g/L,0.46g/g dry material (DM), and1.55g/L/h, respectively, were obtained within72hours. The enzyme cost using the commercial glucoamylase as inulinase was compared to that using the typical inulinase and a large profit margin was identified. The results provided a practical way of Jat application for lactic acid production using cheap commercial glucoamylase enzyme.Finally, corn stover was used as the raw materials for lactic acid production using the same strain P. acidilactici DQ2through the newly developed dry biorefinery processing technology. The effect of the inhibitor removal intensity by the biodetoxification strain Amorphotheca resinae ZN1on the lactic acid fermentation of P. acidilactici DQ2was carefully investigated. Different amount of inhibitor residues in the pretreated corn stover materials severely affected the performance of lactic acid fermentation. The complete removal of all the inhibitor substances after7-10days of bio-detoxification led to the higher lactic acid yield and titer in the simultaneous saccharification and lactic acid fermentation process. The effect of disk milling of the pretreated corn stover on the lactic acid fermentation was also investigated. After the deep biodetoxification and disk milling, the SSF at48℃, pH5.5, and25%(w/w) solids loading in5L of helical agitatedbioreactor resulted in the lactic acid titer, yield, and productivity of74.2g/L,59.76%, and1.03g/L/h, respectively. The result provided a practical process option for cellulosic lactic acid production using agro-lignocellulose residual in the chain of biomaterial resources.Conclusively, the biorefinery processing technology of inulin and lignocellulose biomass for production of lactic acid were established with high lactic acid titer and yield using new microorganisms and new processing technology in this thesis. These studies paved the way of industrial application of value added chemicals from cheap and abundant agricultural biomass.