Study on Soild State Anaerobic Fermentation of Cottonseed Meal to Reduce the Content of Free Gossypol
|School||Anhui Agricultural University|
|Course||Agricultural Products Processing and Storage|
|Keywords||raw cottonseed meal Enterococcus faecalis free gossypol solid-statefermentation|
China is rich in cottonseed meal. Annual output is more than6.0million tons, rankingfirst in the world. Cottonseed meal is an important plant protein with high content of crudeprotein (38％-50％) and a large quantity of amino acid, only lysine is lower than that ofsoybean meal. Cottonseed meal also have plenty of anti-nutritional factors, such as freegossypol, Non-starch polysaccharides, phenolic acid, tannin etc. These anti-nutritionalfactors affect the palatability and the feed intake, decrease the effective availability ofnutritional components, especially free gossypol products is toxic. When animal feed thediets with high content free gossypol, The animal body cell vascular, nerve will bedestroyed, which leads to degeneration and necrosis of animal organs, dysfunction, anddamages the spermatogenic epithelium, reduce animal reproductive ability and even causeinfertility. Microbial fermentation can effectively remove the anti-nutritional factors andimprove nutritional value of cottonseed meal. At present, more researches are aerobicfermentation of cottonseed meal. However, nutrient substances of cottonseed meal wereserious loss in the aerobic fermentation process and autoclave processing will significantlyaffect its nutritional value. While researches on the anaerobic microbe in cottonseed mealfermentation process are related less. This study was carried out by Enterococcus faecalisEF-24from the laboratory preserving strains with a good free gossypol degradation effect.Culture conditions of Enterococcus faecalis EF-24were optimized and free gossypol incottonseed meal was used as the main indicators to optimize their anaerobic fermentationconditions. the degradation mechanisms of free cotton phenol was explored.1Screening and physiological and biochemical identification of the free gossypoldegradation strains. In order to obtain strain for degradation free gossypol in cottonseedmeal,22strain preserved by the laboratory were screened through a gossypol acetic acidmedium. Then, Enterococcus faecalis EF-24was obtained by rescreening of solid-statefermentation with good degradation of free gossypol. EF-24was identified asEnterococcus faecalis by biolog microbial identification system. The credibility is up to97%.2Optimization of Solid-state anaerobic fermentation conditions of cottonseedmeal. To reduce furthest the content of free gossypol of solid-state fermentation rawcottonseed meal with Enterococcus faecalis, the condition of solid-state fermentation wasoptimized by response surface method. The principal fermentation factors including ratio of material to water, initial pH, fermentation time, inoculation amount, fermentationtemperature by single factor analysis. Based on the results of single factor experiment,important factors affecting the content of free gossypol in cottonseed meal were ratio ofmaterial to water, initial pH and fermentation time. After that, the optimum fermentationconditions for free gossypol degradation were confirmed by Box-Behnken experimentaldesign. The results showed that under the condition ratio of material to water1:0.53, initialpH6.57, fermentation time3.06days, inoculation amount4%, fermentation temperature37℃, the content of free gossypol in cottonseed meal was231.68mg/kg and thedegradation rate of free gossypol was67.85%.3Studying the mechanism of degradation free gossypol of solid-state anaerobicfermentation cottonseed meal. There are two ways in microbial fermentation cottonseedmeal degradation free gossypol.(1) Some enzymes of microbial secreting can degrade freegossypol.(2) The free gossypol combined with amino acids with microbial secreting toform bound gossypol, especially lysine and the free amino of active protein. This studyinvestigated the relationship of free gossypol, bound gossypol, total gossypol infermentation process. The results showed that free gossypol degradation with Microbialwas the outcome of microbial enzymes and not free gossypol was transformed to theformation of bound gossypol.