Lactic Acid Production from Agro-Industrial Wastes Using Lactic Acid Bacterial Isolates
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Date
2020-07-07
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Addis Ababa University
Abstract
Lactic acid is a chemical compound that plays an important role in food, pharmaceutical, cosmetics, chemical and polymer industries. It can be produced either through fermentation or chemical synthesis methods. Hence, the objective of this study was production of lactic acid from the fermentation of spent grain of beer and banana peels using indigenous lactic acid bacteria isolated, screened and selected during this study. The effects of temperature, pH, carbon sources, nitrogen sources, and incubation period and inoculum size on lactic acid production during the fermentation processes were also studied. From a total of 90 lactic acid bacteria isolated from ergo and siljo, 66 (84.4%) and 14 (15.6%) LAB isolates were found producing 7.30 to 15.91 and 16-25.2 g/l LA at 48 hrs from 5 ml of MRS broth, respectively. Out of the 14 isolates AS1S that produced the highest amount LA (23.35g/l and 25.20 g/l at 24 and 48 hrs, respectively) from 5 ml MRS broth was selected and subjected to further analysis of LA from produced spent grain of beer (SGB) and banana peel (BNP) during this study. The moisture, ash, protein, fat, fiber and carbohydrate contents SGB and BNP were shown as 7.38% and 5.08%, 3.85% and 5.09%, 4.70% and 6.65%, 3.11% and 1.70%, 4.41% and 12.65%, and 76.56% and 66.59% respectively. The proximate analysis result exhibited that the substrates were nutritionally rich enough to be used as medium to grow lactic acid bacteria to produce LA. During this study the optimum conditions for production of the maximum amount of LA (27.73 and 25.98 g/l from SGB and BNP, respectively), and were obtained at a temperature, pH, nitrogen content, carbon source, and inoculum size of 37 ᵒC, 5.5, 15 g/l NH4)2SO4, 50 g/l glucose and 5% at 72 hrs in that order. The results of this study displayed the potential use of indigenous microbial resources for producing high value biotech products like lactic acid from locally available agro-industrial wastes.
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Keywords
Lactic Acid, Banana Peel, Spent Grain of Beer, Lactic Acid Bacteria