The Production Of Probiotics From Caragana Korshinskii Biomass Through Solid-State Fermentation

Caragana korshinskii,as an important plants for afforestation in arid and desert areas,plays a significant role in wind prevention,sand fixation,and soil water conservation.Bacillus subtilis is one of the major microbial strains for produce probiotics through solid-state fermentation.Increasing the number of spores and viable cells is significant to promote the quality of B.subtilis probiotics.In this study,Caragana korshinskii biomass was employed to produce probiotics.The changes in physical and chemical properties and their effects on bacterial growth and spore formation were analyzed during the solid-state fermentation with B.subtilis.Analysis of the effects of different biomass characteristics on budding spore formation and microecological formulation efficacy by studying the expression of key regulatory genes of budding spore formation.The main results are as follows:(1)Solid-state fermentation could effectively change the physical structure of solid media.The results of low-field nuclear magnetic resonance and specific surface area indicated that microorganisms destroyed macromolecules in the substrate during the fermentation process,exposed hydrophilic groups,expanded pore and cavity volumes,and provided more effective space for microbial growth.The crystallinity results indicated that the natural structure of cellulose had changed.Microbial metabolism degraded the cellulose in the amorphous and partially crystalline areas,resulting in an exposure of the crystalline areas and increase in absorption peak intensity.The infrared spectroscopy results suggested that the characteristic peak intensities of cellulose and lignin were changed during the fermentation process.Lignin and sugar components were damaged,which was beneficial for the microbial utilization.(2)Caragana korshinskii branch was more suitable for improving the solid-state fermentation performance with B.subtilis compared to the wheat bran and Caragana korshinskii flower.After fermentation for 72 h,the viable bacterial number reached the maximum value of 7.85×10~9 CFU/g dry medium in Caragana korshinskii branch culture,which was 3.10 and 1.60 times higher than that in wheat bran and Caragana korshinskii flower medium,respectively.After fermentation for 72 h,the spore number reached the maximum value of 7.30×10~9 CFU/g dry medium in Caragana korshinskii branch culture,which was 2.86 and 1.61 times higher than that in wheat bran and Caragana korshinskii flower medium,respectively.The spo0A gene and sigma genes were key regulatory factors for spore formation.The expression levels of spo0A gene at the 72 h of fermentation in Caragana korshinskii branch medium was2.09 and 1.20 times higher than the maximum values in the wheat bran and Caragana korshinskii flower medium,respectively.The sig E gene expression levels at the 72 h of fermentation in Caragana korshinskii branch medium was 2.25 times and 1.01 times higher than the maximum values in the wheat bran and Caragana korshinskii flower medium,respectively.(3)Through a comprehensive analysis of the viable cell number,spore number,substrates,physicochemical properties,and expression levels of key regulatory factors related to spore formation,it could be concluded that the fermentation performance on the Caragana korshinskii branch was better than that on the wheat bran and Caragana korshinskii flower.This study provides technical support for the production of B.subtilis probiotics utilizing lignocellolosic biomass.