Production of Microbial Pigment from Brewers Spent Grain by Solid State Fermentation
Project no. 21067 · Status: Kapanmış · 2019
Summary
The object of this study is to produce microbial pigment from Monascus purpureus by solid-state fermentation using brewers’ spent grain and waste wafer sheets as substrate. Brewers’ spent grain is generated in large quantities in the brewing process and is often used as low-value animal feed. Waste wafer sheets are broken, crumbled, and wrongly cut wafer sheets that can not be evaluated economically in wafer production facilities. Our results showed that the best pigment yield was found with brewers’ spent grain and wafer sheet mixed in a ratio of 1:4 (w/w) when used as a substrate for pigment production. Moistening agent, initial moisture content, initial pH, inoculum size, and incubation temperature, which are essential factors in solid-state fermentation, were optimized for maximum pigment synthesis. Monosodium glutamate, mineral salt solution, and deionized water have been tested as moistening agents. The effect of initial moisture content (50-90%), pH 5.5-8.5, inoculum size (0.5 mL-4 mL) and temperature (26-32°C) on Monascus pigment synthesis have been examined. Although the best pigment yield was obtained when MSG and mineral salt solution were used together, deionized water which gave similar pigment yields was used as moistening agent to decrease the process cost. The solid-state fermentation of brewers’ spent grain and waste wafer sheets was carried under the optimized conditons of 85% initial moisture content, initial pH 7.5, inoculum size of 3 mL at 28°C. The highest red pigment yield of 59.55 ± 1.85 AU500 / g was obtained at the the 9th day of fermentation. This is the first study that uses solid-state fermentation technique in Monascus pigment synthesis using brewers’ spent grain and waste wafer sheets as substrate.