Research On Bacillus Natto Microecological Preparation By Using Rice Bran As The Matrix

Bacillus natto, which was separated from food, is one of the healthy and ideal strainsto produce probiotics. Rice bran is a kind of by-product in rice processing with lowutilization. To open a new road for developing and utilizing rice bran, also improve theresearch and development of bacillus natto microecologics, in this paper, rice bran wasfirstly hydrolyzed with enzyme, and then the hydrolysate and residue of rice bran wereused to ferment bacillus natto, some relevant technological conditions were optimized,the results were as follows.1、α-amylase and glucoamylase could be combined to hydrolyze starch in rice bran. Theoptimal technological liquefying conditions of rice bran starch were optimized in thisstudy through the single factor and the L9（34）orthogonal experiment, results were asfollows: solid-liquid rate1:5, pH value6.0, the added content of α-amylase16u/g,temperature60℃,the added content of CaCl₂0.2%. Under these conditions, theliquefying DE values of starch in rice bran was24.31%. According to the single factorand the L16（45）orthogonal experiment, the optimal technological saccharifyingconditions of rice bran starch were optimized, results were as follows: solid-liquid rate1:5, pH value4.0, the added content of glucoamylase200u/g, temperature60℃, time6hours. Under these conditions, the saccharifying DE values of starch in rice bran was98.96%.2、Celluase and papain could be combined to hydrolyze protein in rice bran. Thepreprocessing conditions of celluase were as follows: solid-liquid rate1:10, pH value4.8,the added content of celluase200u/g, temperature60℃, time2hours. According to thesingle factor and the L（934）orthogonal experiment, the optimal technological hydrolyzingconditions of papain were as follows: solid-liquid rate1:10, pH value8.0, the addedcontent of papain1000u/g, temperature60℃,time2hours. Under these conditions, theextraction rate of protein in rice bran came up to69.19%.3、To the hydrolysate of rice bran as the basic fermentation medium, through the singlefactor and the L9（34）orthogonal experiment, the optimal proportion of culture mediumwere as follows: the hydrolysate of rice bran, the added content of NaCl0.50%, the addedcontent of （NH₄）₂SO₄0.50%. The optimal conditions of culture were temperature35℃,pH value7.5, loaded liquid50mL/250mL, inoculation quantity4%, time24hours. Underthese conditions, the viable count of bacillus natto was2.34×10⁹cfu/mL, which was2.23times more than before. To the hydrolyzing residue of rice bran as the basic fermentationmedium, through the single factor experiment, the optimal proportion of culture mediumwere as follows: the hydrolyzing residue of rice bran, the added content of glucose2.0%,NH4NO30.5%, moisture content60%. The optimal conditions of culture weretemperature35℃, inoculation quantity8%, time5days. Under these conditions, the viable count of bacillus natto was4.05×10¹⁰cfu/g, the count of its spore was1.81×10¹⁰cfu/g.4、Single factor experiments to study different cryoprotectants impact on survival ofvacuum freeze-drying. Skim milk, ascorbic acid and maltodextrin were chosen tocompose the cryoprotectant. Then through L9（34）orthogonal experiment, the optimalcomposition of cryoprotectant was as follows: skim milk15.0%, ascorbic acid0.3%andmaltodextrin5.0%. Under these conditions, the viable rate of bacillus natto was up to71.57%, the viable count of vacuum freeze-drying was up to8.23×10⁹cfu/g, the count ofits spore was up to5.62×10⁹cfu/g. The product could present better stability after beingconserved for2month under room temperature，4℃and-18℃. The solid statefermentation product was dried in a vacuum oven, the viable count of bacillus natto was6.33×10¹⁰cfu/g, the count of its spore was2.61×10¹⁰cfu/g, the activity of protease was4352u/g. The product could present better stability after being conserved for30daysunder room temperature，4℃and-18℃.