Lactic Acid Production from Apple Skin Waste by Immobilized Cells of Lactobacillus reuteri
Apple skins generally are not used in food products and often are discarded as waste. Apple skin contains several useful nutrients particularly sugars and more complex carbohydrates. This study was undertaken to determine the feasibility of apple skin waste as a media source for the production of lactic acid (LA) using Lactobacillus reuteri. One to nine ratios (10%) of apple skin to water was boiled for 5 min and its filtrate was then added with each of following supplements, respectively; ammonium phosphate, manganese sulfate, peptone, yeast extract, and potassium phosphate monobasic and dibasic. The efficacy of apple skin filtrates with and without supplements was determined by measuring pH, glucose and lactic acid after 2, 4 and 8 h fermentation at 37°C. Moreover, apple skin filtrate was also compared with MRS broth and G-M17 broth for the efficacy of glucose utilization and LA production. At the end of 8 h incubation, pH of apple skin filtrates with peptone and yeast extract reduced from 7 to ∼4. The LA concentrations produced from the filtrates with either peptone or yeast extract supplement were the greatest ranging from 0.9 g/L to 1.9 g/L. The efficacy of LA production using apple skin filtrate was about the same as G-M17 broth. Higher amount of LA was yielded with media inoculated with immobilized (encapsulated) cells than free cell. Results also indicated that immobilized L. reuteri MM2-3 produced 40% higher amount of LA than free cell. The results obtained from this study indicate that apple skins as a carbohydrate source and immobilization of lactic acid bacteria (LAB) could be a promising method for the production of LA. Further study is necessary to identify ways to increase glucose availability and promote LAB growth and LA production.
KeywordsLactic Acid Lactic Acid Bacterium Polylactic Acid Free Cell Lactic Acid Production
This research was supported in part by a grant from the Egyptian scholarship and funds allocated to North Carolina Agricultural and Technical State University through the Cooperative State Research, Education and Extension Service of the United States Department of Agriculture, Project No. NC.X-173-5-02-170-1. Partial fund was provided by the Nutritional Analysis Service Laboratory at SIUC, Carbondale, IL. The authors also would like to express gratitude to Dr. C.S. Turner, Associate Dean for Research for her support and Dr. K.J. Gruber for his suggestions on this manuscript.
- Magnuson, J. K., and L. L. Lasure. 2004. “Organic acid production by filamentous fungi.” In: J. S. Tkacz and L. Lange (Eds.). Advances in fungal biotechnology for industry, agriculture, and medicine. Kluwer Academic/Plenum Publishers, New York, pp. 207–340.Google Scholar
- Naveena, B. J., M. Altaf, K. Bhadrayya, and G. Reddy. 2004. Production of L(+)-lactic acid by Lactobacillus amylophilus Gv6 in semi-solid state fermentation using wheat bran. Food Technol. Biotechnol. 42, 147–152.Google Scholar
- Wee, Y. J., J. N. Kim, J. S. Yun, D. H. Park, and H. W. Ryu. 2006. Pilot-scale lactic acid production via batch culturing of Lactobacillus sp. RKY2 using corn steep liquor as a nitrogen source. Food Technol. Biotechnol. 44, 293–298.Google Scholar
- Word markets and trade. 2007. World apple situation. May. http://www.fas.usda.gov/htp/ horticulture/Apples/World_Apple_Situation_053107.pdf