Enhanced Lactic Acid Production from Hydrolysed Sago Starch by using Different Types of Nitrogen Sources by Lactococcus lactis 10-1

Nur Fashareena Adila, Abd Rahim (2017) Enhanced Lactic Acid Production from Hydrolysed Sago Starch by using Different Types of Nitrogen Sources by Lactococcus lactis 10-1. Masters thesis, Universiti Malaysia Sarawak (UNIMAS).

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Abstract

LA is extensively being used in the field of phannaceutical, food, chemical, cosmetic and in the production of biodegradable plastic polyLA (PLA). Nitrogen sources such as corn steep liquor (CSL), ammonium sulphate (AS) and urea were tested individually and incorporate with each other with the purpose to stimulate the LA fennentation in comparison with the use of yeast extract (YE). The objective was to reduce the production cost ofLA without affecting the . concentration of LA production by using sago starch as an alternative substrate. The fermentation media consisted of hydrolysed sago starch at an optimum concentration (110 gLI), supplemented with various tested ofnitrogen sources and was inoculated with Lactococcus lactis 10-1. Batch fennentation was carried out by controlling the pH (6.8), temperature (45°C) and agitation (100 x g) in 2 L jar fennenter. Based on the results obtained, 20 gL- 1 of YE supplementation proved to be the most optimum concentration of YE to be supplied into a fermentation media as compared to different concentrations of YEo The LA production was 96.3 gL1 , and the residual glucose was 2.95 gL-I • None of the individually tested nitrogen sources gave LA concentrations comparable to 20 gL-1 YE supplementation. However, the mixture ofnitrogen sources was comparable to the production of LA produced by 20 gL- 1 YEo The concentration of LA production by the mixture of ammonium sulphate: corn steep liquor: yeast extract (AS: CSL: YE) with the ratio of 2:2: 1 was 94.5 gL- 1 with the residual glucose of 4.55 gL-I. The incorporation of AS, CSL and YE generate comparable performance with the medium supplemented only with YE (20 gL- 1 ) and was not statistically different (p>0.05). The results indicated that this mixture ofnitrogen sources could be economically used to minimise the use of YE without affecting the concentration of LA.

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