engleski

Study on spent brewer's yeast hydrolysis by acid

In this study, acid induced autolysis of spent brewer's yeast was carried out with sulfuric (SA) and lactic acid (LA). The aim of this study was to estimate the success of autolysis induced with inorganic acid compared to autoysis induced with organic acid. The reaction was performed at pH and temperature range which enable the optimum activity of the yeast endoenzymes, so that the process can be considered on acid induced autolysis of yeast biopolymers. Process of hydrolysis was monitored by measuring the increase in the free amino nitrogen (FAN, -amino N) concentration. Hydrolysis with sulfuric acid was conducted at the temperature range T = 45 - 60 °C, pH 5.0 - 5.4 and in the period of 12 - 32 h. Hydrolyses with lactic acid was carried out at the temperature range T= 48-62 °C, pH 4.8-6.0 and in the period of 12-44 h. The best results (FAN = 4917.45 mg/L) obtained with SA were at the following process conditions: T=52 °C, pH = 5.2 and t = 32 h. On the other hand, the best results (γFAN = 5789.36 mg/L) obtained with LA were at the T=55 °C, pH = 5.5 and t=44 h. In both performed acid hydrolysis, -amino N content was not detected at temperatures higher than 60 °C, suggesting the possible inactivation of yeast proteases

yeast autolysis induced with acid; free amino nitrogen (FAN; -amino N)

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