LACTIC ACID PRODUCTION BY LACTOBACILLUS DELBRUECKII FROM AGRICULTURAL WASTE: ROLE OF C:N RATIO AND DIFFERENT CARBON AND NITROGEN SOURCES

Background and Aim:Lactic acid and its derivatives are widely used in the food, pharmaceutical, leather and textile industries. There are two main routes for producing lactic acid; synthetic route through hydrolysis of lactonitrile and microbial route through fermentation of carbohydrates using lactic acid bacteria (LAB). The aim of this study was to investigate the effect of C:N ratio and different carbon and nitrogen sources on lactic acid production by lactobacillus delbrueckii from agricultural waste.Methods:Lactobacillus delbrueckii PTCC 1333 was obtained from the Iranian Research Organization for Science and Technology (IROST). In this work, design of experiments (DOE) methodology using full factorial design was applied to evaluate the influence of C:N ratios (10, 20 and 30), different carbon sources (corn, rice and potato waste) and nitrogen sources (ammonium sulfate, ammonium nitrate, peptone and yeast extract) on lactic acid production. The fermentation process was held at a temperature of 37 °C for 48 hours. Lactic acid contents in fermentation broth were analyzed by high pressure liquid chromatography (HPLC) system.Results:The highest Lactic acid production (61.18 g/l) was achieved in C:N ratio of 10:1, corn waste as a carbon source and yeast extract as a nitrogen source.Conclusion:The results showed that C: N ratio is another important factor that affects lactic acid production that needs to be optimized in the main component of the medium. Also, corn waste due to natural sources of protein and high starch content is a good and cost-effective substrate for lactic acid production.

کلیدواژه ها:

Lactobacillus delbrueckii ، Yeast extract ، Agricultural waste ، HPLC