Study On Producing Rapeseed Peptide By Mixed Solid-State Fermentation

Rapeseed meal which is rich in protein is the by-products of rapeseed oilproduced，and it is an important resource of plant protein．However，because ofrapeseed meal containing glucosinolates，phytic acid，tannins and other anti-nutritionalfactors to reduce its nutritional value，the use of rapeseed meal is limited．Rapeseedpeptide is a mixture of small molecular peptides hydrolyzed from rapeseed protein，Itpossesses better processing characteristics and biological activities than rapeseedprotein，and have broad application prospect in feed additives，food and medicine.Microbial fermentation is one of the ways to produce rapeseed peptides．On the onehand it combines the productions of the protease fermentation with the rapeseedpeptide enzymolysis，this method reduced the cost；the other hand it combines theproduction of rapeseed peptide fermentation with the study on detoxification ofrapeseed meal，it is because that microbial fermentation of rapeseed meal has adetoxification effect．It lay a basis of the application for truely promoting efficient useof resource of plant protein and feed safety of plant protein oligopeptides．In this study，industrial by-products rapeseed meal was used to produce rapeseedpeptides through the mixed microbial solid-state fermentation，and the purpose is toobtain the fermentation product that have high content of rapeseed peptides and lowcontent of glucosinolates，and that can be used as feed additives which applied to feedindustry．This study focused on the following four aspects：(1) Screening of strains forproducing rapeseed peptides through mixed solid-state fermentation；(2) Study ondetoxification through mixed solid-state fermentation on rapeseed meal；(3)Optimization of medium conditions for producing rapeseed peptides through mixedsolid-state fermentation；(4) Optimization of fermentation conditions for producingrapeseed peptides through mixed solid-state fermentation．The specific results showedas follows：(1) The compatibility was obtained by combining two kinds of bacteria withBacillus subtilis and Bacillus licheniformis respectively with three kinds of fungi withActinomucor elegans，Aspergillus usamii and Aspergillus oryzae，and the propermicrobial strain for producing rapeseed peptides from rapeseed meal by solid-statefermentation was obtained by means of plate cultivation and mixed fermentation．Theresults showed that the mixed strain of Bacillus subtilis and Actinomucor elegans hasthe best effect of mixed fermentation，and the content of low molecular weight rapeseed peptides which were produced after mixed fermentation was higher thanthose of other two mixed strains，and it was more suitable for producing rapeseedpeptide through mixed solid-state fermentation．(2) The solid-state fermentation on rapeseed meal by three kinds of straincombinations which have better compatibility was based on plate cultivation inscreening of srains for producing rapeseed peptides through mixed solid-statefermentation，and the effects of mixed fermentation on glucosinolates degradationcould be evaluated by rate of glucosinolates degradation．The results showed thatmixed solid-state fermentation by Bacillus subtilis and Aspergillus usamii has thehighest rate of glucosinolates degradation，and the rate of glucosinolates degradationcould reached81.67%under the condition of inoculation ratio for2:1．The mixedstrain of Bacillus subtilis and Aspergillus usamii has better effect of mixed solid-statefermentation on glucosinolates degradation than those of other mixed strains．(3) Rapeseed meal was used to produce rapeseed peptides through mixedsolid-state fermentation with Bacillus subtilis and Actinomucor elegans． Withrapeseed peptide recovery ratio，index of soluble nitrogen and rate of glucosinolatesdegradation as the indexes，the medium conditions were obtained by single factor testpreliminary，then according to the Box-Benhnken center united experimental designprinciples based on the single factor test，and establishing the regression equation onrapeseed peptide recovery ratio versus the influencing factors to optimize mediumcomposition through response surface analysis．Results showed that the optimalconditions were as follows：wheat bran amount5%in rapeseed meal，solid-liquid ratio1:1.35，glucose amount0.50%，KH2PO4amount0.36%，initial pH6.5．Under theabove conditions, the rapeseed peptide recovery ratio of fermentation product couldreach6.85%，and the rate of glucosinolates degradation reached62.09%．(4) The craft conditions which were based on optimization of medium conditionscould be further optimized for producing rapeseed peptides through mixedsolid-state fermentation by Bacillus subtilis and Actinomucor elegans．With rapeseedpeptide recovery ratio， index of soluble nitrogen and rate of glucosinolatesdegradation as the indexes，the fermentation conditions were obtained by single factortest preliminary，then according to Box-Behnken central composite experimentaldesign，the fermentation conditions were further optimized by response surfaceanalysis which is based on the single factor test．Results showed that the optimalconditions were as follows： simultaneously inoculating Bacillus subtilis and Actinomucor elegans，inoculation ratio for4:1，fermentation temperature32.1℃andfermentation time4.64d(111h)．Under the above conditions，the rapeseed peptiderecovery ratio of fermentation product could reach9.85%，which was relativelyincreased by43.8%compared with the result of optimization of medium conditionsand98.6%compared with the result of un-optimized，the effect of optimizingconditions of the fermentation was significant．At the same time，the rate ofglucosinolates degradation reached67.83%， the effect of mixed solid-statefermentation after optimization on glucosinolates degradation has improved comparedwith the result of un-optimized．...