توصيفگر ها :
پساب خميرمايه , ويناس , آب پنير , COD , قارچ هاي رشته اي , زيست توده قارچي , كشت قارچي , هضم بي هوازي , اسيد هاي آمينه , پروتئين , كيتوزان
چكيده انگليسي :
Effluents from fermentation and food industries are the sources of various environmental challenges. Molasses is a common feedstock for fermentation industries, including baker's yeast and ethanol, leaving a huge volume of acidic, dark brown, and strong odor wastewater with high COD content, called vinasse. Tens of millions tons of whey with high organic content are also generated annually in the dairy industry. A significant part of these wastewaters are unused and their treatment imposes heavy costs on industries. The integration of baker's yeast wastewater, vinasse, and whey for an innovative two or three-step waste biorefinery process by producing protein-rich fungal biomass and biogas along with COD and nutrients removal was the main object of the present research. The experiments performed in this study were divided into four separate parts. 1- First part: Four strains of filamentous fungi (i.e., M. indicus, M. hiemalis, N. intermedia, and A. oryzae) were cultivated in baker's yeast processing wastewater. The cultivation of A. oryzae on wastewater resulted in a higher biomass production compared to the other three fungal strains. The maximum fungal biomass yield was 5.13 g/L. Overall, 1 m3 of baker's yeast wastewater yielded 5.13 kg of fungal biomass containing 43.8% (w/w) crude protein and 1.42 m3 of methane. In addition, using this two-step biorefinery, COD was reduced by 58.7% from 29.1 to 12 g/L. 2- Second part: The two-stage fungi-based biorefinery for protein and biogas production from vinasse and whey using N. intermedia was conducted. In the first stage, N. intermedia cultivation conditions including ratio of vinasse to whey (with ratios of 100: 0, 75:25, 50:50, 25:75, 0: 100 (v/v)), pH (4.5, 5.5, and 6.5), cultivation time (48, 72, and 96 h), and nutrient supplementation were optimized in a sequential order. Under optimum conditions (pH 6.5, cultivation time of 96 h and vinasse to whey ratio 25:75 (v/v) with nitrogen source supplementation), 12.0 g/L fungal biomass was produced. In the second stage, the remained effluent after fungal fermentation was subjected to anaerobic digestion. Overall, 1 m3 of wastewater yielded 12.0 kg of fungal biomass containing 45.0% (w/w) crude protein and 10.3 m3 methane, accompanied by 93.3% COD removal. 3- Third part: M. indicus cultivation conditions on vinasse were optimized using the Box–Behnken model. The maximum biomass yield of 7.85 g/L was attained. Chitosan in the fungal cell wall was extracted and 0.104 g of chitosan/ g biomass was obtained. Overall, 1m3 of vinasse at optimum conditions yielded 0.82 kg chitosan and 8.2 m3 methane. In addition, during this two-step process, COD was reduced by 92.0%. 4- Forth part: The three-stage fungi-based biorefinery on vinasse and whey using A. oryzae was conducted. Like the second part, the A. oryzae cultivation conditions on vinasse and whey were optimized first. Under optimum conditions, 15.7 g/L fungal biomass was produced. In the second stage of this process, N. intermedia was cultivated on the effluent of A. oryzae cultivation and the biomass yield of 2.56 g/L was obtained. In the third stage, the fungal cultivation effluent in the second stage was used to produce biogas. Overall, 1 m3 of wastewater yielded 17.75 kg of fungal biomass (containing 9.51 and 0.84 kg crude protein and lipid, respectively) and 5.0 m3 methane, accompanied by 96.5% COD removal. In addition, fungal biomass produced in the first, second and forth parts was analyzed to determine the amino acid and fatty acid profiles for comparison with soybean meal and fishmeal as the most commonly used protein sources in aquafeed. Therefore, besides addressing the environmental issues of baker's yeast wastewater, vinasse, and whey, the fungi-based biorefinery could successfully produce value-added products.
