Enhanced isomer purity of lactic acid from the non-sterile fermentation of kitchen wastes

• Published in: Bioresource technology Vol. 99; no. 4; pp. 855 - 862
• Main Authors: Zhang, Bo, He, Pin-jing, Ye, Ning-fang, Shao, Li-ming
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.03.2008; [New York, NY]: Elsevier Ltd; Elsevier
• Subjects: Biological and medical sciences; Bioreactors - microbiology; Biotechnology; Clostridium; Computer Simulation; Fermentation; Fermentation time; Food industries; Food Microbiology; Fundamental and applied biological sciences. Psychology; Hydrogen-Ion Concentration; Industrial Waste - prevention & control; Isomer purity; Isomerism; Kitchen wastes; Lactic acid; Lactic Acid - chemistry; Lactic Acid - metabolism; Lactobacillus - metabolism; Methods. Procedures. Technologies; Microbial engineering. Fermentation and microbial culture technology; Models, Biological; Restaurants; Sterilization; Temperature; Use and upgrading of agricultural and food by-products. Biotechnology; pH; Temperature; Lactic acid; Isomer purity; Kitchen wastes; Fermentation time; Food waste; Purity; Fermentation; Isomer
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2007.01.010

In order to improve the purity of lactic acid isomers, the effects of pH, temperature, fermentation time and their interactions on l(+) or d(−)-lactic acid production were evaluated during lactic acid fermentation of the non-sterile kitchen wastes. The results showed that l(+)-lactic acid was the main isomeric form. The isomer purity was much higher at acidic or alkalic pH (non-controlled pH, pH 5 and pH 8) than neutral pH (pH 6 and pH 7). Increasing the fermentation temperature from 35 °C to 45 °C at pH 7 enhanced the isomer purity from 60:40 to 83:17. The optimal fermentation time for the purity of lactic acid isomers was found to depend on the corresponding pH and temperature. From the response surface analysis, the optimized combination of pH and temperature could obviously increase the l(+)-isomer concentration. It is confirmed that the variation of the isomer purity with pH, temperature and fermentation time change resulted from the substitution of microbial community composition. The lactic acid bacteria and Clostridium sp. dominated the fermentation of non-sterile kitchen wastes, and the emergence and disappearance of lactic acid bacteria which produced l(+)-isomer and Clostridium sp. resulted in the variations of the isomer purity.