Production of Monascus Pigments from Brewer’s Spent Grain and Determination of Its Stability
Project no. 736 · Status: Kapanmış · 2016
Summary
The production of natural color substances from alternative and inexpensive sources has been studied in the last years. The aim of this study is to produce red pigment by using Monascus purpureus from brewer’s spent grain which is an important waste originated from brewery industry. Brewer’s spent grain is a lignocellulosic raw material that is resistant to hydrolysis. Therefore in the first part of this thesis, different hydrolysis and subsequent detoxification methods were applied on brewer’s spent grain in order to make it available for Monascus purpureus. Among the methods used, the highest pigment production was obtained by hydrolysis using H2SO4 and subsequent detoxification with Ca(OH)2 . The effect of parameters such as acid concentration in hydrolysis, dilution rate, initial medium pH, fermentation volume, inoculum amount nitrogen source and microorganism strain on pigment production were determined by one variable at a time optimization method. The maximum pigment production of 22.25 UA was obtained when brewer’s spent grain diluted in [1:6] (w/w) acid solution and hydrolyzed using a concentration of 2% (w/v) H2SO4 and inoculated with 2% (v/v) mold spores at 50 ml of the fermentation medium volume with an initial pH of 5.5, 8 g L-1 of monosodium glutamate (MSG) was used as the nitrogen source. The importance levels of media components used in pigment production were determined by Plackett-Burman design method. It was found that monosodium glutamate and zinc sulphate (ZnSO4.7H2O) were statistically significant in the production of red pigment. In the final stage of the study, pigment production in different stirrer speed and aeration rate combinations in stirred tank bioreactor was performed. The maximum pigment production values of 20.21 UA (red), 21.01 UA (orange) and 25.75 UA (yellow) were obtained at variable stirrer speed (first five days 100 rpm, last three days at 200 rpm) and variable aeration rate (1 vvm for the first three days, 0.5 vvm for the last 5 days) values. Stability of the produced pigment against heat and different pH values was tested. It was determined that the pigment was able to maintain a significant degree of stability (> 92%) at pH 6.0 and 40 °C up to 360 min, at pH 8.0 and 80 °C up to 180 min (>85%). This is the first study that investigates in detail, the use of nutrient-rich brewer’s spent grain derived hydrolysate in the production of red pigments from Monascus purpureus in submerged fermentation.