Breeding Of Highly Effective Degrading Microorganisms For Ricinine And Optimization Of Fermentation Conditions By Mixed Strains

A new type of high-quality protein feed resource-castor bean meal is brought about by the development of castor industry. Its rich protein, amino acids and minerals are major bright spots in fodder development. However, ricinine and allergen limits its application. Especially ricinine, which is a highly toxic alkaloid, causes much difficulty in degradation treatment. In this article, a strain of bacteria with highly effective degradation of ricinine was isolated from spoiled castor cakes and yeast with good detoxification effect was screened from strains in the lab. Mixed fermentation of the two strains was carried out on castor bean meals to degrade ricinine. Optimization of fermentation conditions was performed by single factor test and response surface methodology, through which a quadratic polynomial regression model was constructed to obtain the best processing parameters. Besides, nutrition contrast of castor bean meals before and after fermentation was undertaken, along with a brief analysis in the nitrilase activities of experimental microorganisms.From spoiled castor bean meals, bacteria BPW was isolated with ricinine degradation rate up to67.04%, which was preliminarily identified as the genus Arthrobacter by morphology, physiological and biochemical tests. On the other hand, yeast SJM of genus Candida was screened from degrading strains in laboratory with ricinine degradation rate of66.30%.Mixed fermentation of the two strains above was applied to castor bean meals to achieve ricinine degradation. Single factor experiment and response surface methodology was implemented to attain optimized fermentation conditions through regression model construction with ricinine degradation rate as the response value, which was specified as follows:substrate solid-liquid ratio of2:5, temperature31℃, inoculation ratio (SJM:BPW) of1:1(v/v), total inoculation14.35%(v/w), culture time131h. The ricinine degradation rate can reach94.19%with allergen degradation rate of91.04%. There is no significant change in total protein content of castor bean meals after fermentation.Nitrilase activities of the two strains were analyzed, which showed that strain suspension3mL, pH=7(BPW) or pH=8(SJM), reaction time20min were the best determination conditions of ricinine degradation activity within experimental range, in which BPW degraded about41.59%of ricinine, while SJM reached about39.88%. Amidase was hypothesized containing in both strains with substrate specificity test.