Monascus Purpureus Fermentation Waste Broth Treatment And Co-producing Single Cell Protein Fodder By Chlorella Pyrenoidosa

With the improvement of people’s living standards,the quality and demand for animal-derived products have increased dramatically,and feeding directly affects the quality and production of animal-derived products.Traditional animal and plant protein source feeds have disadvantages such as unbalanced amino acids,poor palatability and high cellulose content.Long-term feeding will affect the flavor and quality of derived products.Therefore,it is particularly important to seek high-quality feed substitutes with balanced nutrition and abundant resources.The advantages of short growth cycle of microalgae,high efficiency of photosynthetic carbon fixation,non-competition with agricultural arable land and rich protein in cells,which have become the dominant resources for the development of new animal feeds.However,the high cost of microalgae cultivation is the main limiting factor for the realization of industrialized large-scale production of microalgae feed.Microalgae can absorb wastewater nitrogen and phosphorus for growth and accumulate intracellular high value-added products,which is an effective way to reduce the cost of microalgae cultivation and make wastewater resources.In this paper,Chlorella pyrenoidosa was used to treat monascus fermenta Monascus purpureus fermentation waste broth to evaluate its treatment effects on nitrogen and phosphorus.At the same time,it investigates the feasibility of low-cost cultivation of Chlorella sp.to co-production of single cell protein feed with Monascus purpureus fermentation waste broth（hereinafter referred to as fermentation broth）.The results obtained are as follows:（1）The ICP-MS characterization shows that the nutrient elements such as N,P,Na,K,and Mg in the fermentation broth are significantly higher than the conventional Basal medium,which is 1.74 to 7.34 times the content of each nutrient element,and the fermentation broth is rich in amino acids(460.8 mg·L^-1),indicating that the fermentation broth is an ideal medium for the growth and metabolism of Chlorella.Chlorella was inoculated in the fermentation broth at a ratio of 8%and treated for 168hours.The removal rate of TN,TP,NH₃-N,COD,and BOD in the fermentation broth was the largest,which were 62.68%,65.16%,97.36%,80.26%,81.23%,respectively.The fermentation broth processing capacity was enlarged to a 10 L photobioreactor,and the removal efficiency of Chlorella to the fermentation broth TP,TN,NH₃-N,COD,and BOD was further improved to 99.5%,95.1%,99.4%,98.2%,99.7%,the effluent index after Chlorella treatment meet the GB 25463-2010 wastewater discharge standard,confirming the feasibility of using Chlorella to treat fermentation broth.（2）Based on（1） dilute the fermentation broth and water to cultivate Chlorella,when the dilution ratio of fermentation broth to water was 8:2,the biomass and protein yield of Chlorella were separately 5.28 g·L^-1and 2.81 g·L^-1.The optimal dilution ratio of fermentation broth was fed-batch to Chlorella to further improve protein productivity and the final biomass and crude protein yield were separately48.53 g·L^-1 and 27.20 g·L^-1,which were 13.08-and 19.85-fold more than Basal medium.The amino acids of Chlorella powder cultured with fermentation broth showed that total amino acids and essential amino acids were 58.56%and 26.44%,and the essential amino acid index is greater than 0.95,which is a high-quality single cell protein sources.The contents of essential minerals potassium,magnesium,iron,calcium and zinc in Chlorella powder were separately 18451.58,9094.79,1916.05,352.46 and 66.38 mg/kg.Fatty acids were mainly composed of C16-C18?（96%）and also the contents of linoleic acid and linolenic were separately 27.06%and25.82%.Synchronously,the indexes of heavy metals and microorganisms of algal powder were fully complied with GB 13078-2017.It was proved that the Chlorella powder cultured in fermentation broth had comprehensive nutrition and was in line with the national standard of feed safety and health.（3）In vitro simulated pig gastrointestinal digestion of dry matter,crude protein,crude fat and starch of Chlorella powder,the digestibility of which is as high as79.02%,90.13%,92.93%and 87.81%.Among them,the digestibility of dry matter and crude protein were roughly equivalent to other commonly used feed raw material protein such as corn and soybean,while the digestibility of crude fat and starch is much higher than that of the above commonly used feeds.The Caco-2 cell line was further used to evaluate the bioavailability of Chlorella powder in the small intestine.The results showed that the cells had a better absorption effect on Chlorella powder polypeptides,triglycerides,free fatty acids and carbohydrates,with absorption rates as high as 60.96%,59.44%,90.85%and 35.22%,respectively.The results confirmed the feasibility of producing high quality single cell protein feed from Chlorella cultured in Monascus purpureus fermentation waste broth.