Substitution of yeast extract by ammonium sulfate for mannitol production in cashew apple juice

Abstract

Abstract The use of agriculture excess as substrate in industrial fermentations became an interesting alternative to reduce production costs and to reduce negative environmental impact caused by the disposal of these products. In this work, the use of cashew apple juice supplemented with ammonium sulfate as substrate for mannitol production by two Leuconostoc strains was studied. The carbohydrates of cashew apple juice are glucose and fructose. Process pH was not significant on fructose conversion into mannitol by Leuconostoc citreum B-742. However, for L. mesenteroides B-512F the process pH showed a significant effect on fructose conversion into mannitol. The use of cashew apple juice supplemented with ammonium sulfate in replacement of yeast extract enhanced the yield L. mesenteroides B-512F was the best mannitol producer. The optimal pH for mannitol production from fructose by this strain in pH-controlled fermentation was at pH 5.0 with mannitol yield of 95% and productivity of 1.6 g/L h. Lactic acid bacteria are known as nutritional exigent microorganisms. Usually, they are cultivated in yeast extract and other complex nitrogen source. Herein, the combination of an inorganic exogenous nitrogen source and the amino acids from the cashew apple juice was enough to support LAB growth in a low cost substrate.