زهرا خزائيلي نجف آبادي

Pigments are widely used in food, pharmaceutical and textile industries. Because of possible limitations in the use of artificial pigments, natural pigments are being developed as alternatives. Microorganisms are one of the best natural sources of pigment production. Monascus purpureus fungus is one of the pigment-producing species that has the ability to produce the highest amount of pigment by using solid state fermentation in a culture medium containing starch. In this research, dried potato peel was used as the culture medium for this fungus. First, preliminary experiments were done to find the best saline culture medium, the concentration and amount of inoculum, as well as the size of the substrate in the shake flasks. Then, by adding a suitable salt culture medium to the dry and crushed substrate and the inoculum, the effect of the two variables of initial substrate moisture content and aeration on the amount of pigment production (red, orange and yellow) and the growth of microorganisms in the laboratory packed bed bioreactor with a volume of 0.127 liters made of polypropylene was investigated. In this experiment, the statistical method of factorial design was used and the humidity at two levels was 55 and 60% and the aeration strategy was at four levels: constant aeration with a flow of 6 liters per hour, constant aeration with a flow of 8 liters per hour, intermittent aeration 12 hours a day and intermittent aeration 18 hours per day was eva‎luated. The change in the initial substrate moisture content did not have a significant effect on the growth rate, but it was effective on the pigment production. The highest amount of pigment production occurred in the initial substrate misture of 55%. Also, the highest fungal growth rate was observed in less aeration, i.e. intermittent aeration 12 hours per day, and the highest pigment production was observed in intermittent aeration 18 hours per day with 55% moisture. According to this research, the optimal conditions for the production of red color, moisture of 55% and intermittent aeration with a flow of 6 liters per hour for 18 hours per day were obtained. Also, the investigation of the stability of the produced pigments shows that this pigment has very good stability in the temperature range of -80 to 40 °C and pH equal to 6 to 8 and the conditions of light, darkness and autoclave.

رنگدانه ميكروبي , قارچ موناسكوس پورپورئوس , بيوراكتور بسترآكنده , هوادهي , رطوبت سوبسترا

Microbial pigment , Monascus purpureus fungi , Packed bed bioreactor , Aeration strategy , Substrate moisture

Zahra Khazaeli

dr Parisa Hejazi