The Study On Optimum Process Parameters For Solid-state Fermentation Of Palm Kernel Meal

In this study，the efficient cellulose degradation strains were isolated and selectedfrom palm kernel cake heap and rotten leaf soil and combined with Saccharomycescerevisiae and Bacillus subtilis to get the optimized process parameters of fermenting palmkernel meal in solid state conditions. The results were shown as follows：Experiment1：47species of strains were accumulated，isolated and purified frompalm kernel cake heap and rotten leaf soil．We firstly screen out the11species of efficientcellulose degradation strains by comparison of hydrolysis ring size．Through furthercomparison of cellulase activity，2species of fungi F1and F2which have high enzymeproduction ability were finally selected．The filter paper activity (FPU) of fungi F1and F2is7.42IU/mL and10.08IU/mL，respectively，and the exoglucanase activity(Cx) is7.42IU/mL and10.08IU/mL，respectively．Identify the colony morphology of the two strains，preliminary judgmentis is that the strain F1was Aspergillus oryzae，and the strain F2wasAspergillus niger．Experiment2：Combined F1and F2strains with Saccharomyces cerevisiae andBacillus subtilis and then get different combination treatments to ferment palm kernel mealin solid state conditions with bran as supplementary material．Take the variation of crudeprotein content of culture medium before and after treatment as the evaluation index todetermine the best strains combination，ratio and inoculation volume．The results showedthat: The best strain combination was＂F2+Saccharomyces cerevisiae＂，the optimalratio was1：1，the optimum inoculation was8%，the crude protein content of fermentationproduct increased by7.21%after fermentation．Experiment3：The content of supplementary material (bran) is10%，15%，20%，25%and30%，respectively．The dosage of nitrogen source (ammonium sulfate) is1%，2%，3%，4%，5%and6%，respectively．The single factor tests have shown that the bestresult of fermenting palm kernel meal in solid state conditions is raising the content ofcrude protein by9.45%with bran and ammonium sulfate in the dosage of20%and4%，respectively．Experiment4：Based on the result of the preliminary test，further study is focused onthe effect of water addition，fermentation temperature and time on the crude proteincontent of the fermentation products．Box-Behnkens response surface method was used toget the result that the best parameters of palm meal solid state fermentation process was： water addition(A)：1.48ml/g，fermentation temperature (B)：35.04℃and fermentationtime(C)：7.34d，and in this situation the theoretical crude protein content would be30.88%(crude protein content=30.688-0.3525A+0.00875B+0.61375C+0.02AB-0.12AC-0.2075BC-0.41275A2-0.77025B2-1.00025C2)，but practical data was30.34%which was inaccord with expectations．Further studies showed that under these best parameters，thecrude protein content of the fermentation products was up to33.49%in the no-sterilizedmedium compared to30.34%in sterilized medium (P<0.05)，and also the crude proteincontent of the fermentation products increased by58.20%compared to21.17%，Argininecontent improved to1.10%compared with0.24%，and increased by103.53%，Crude fatcontent decreased to4.82%compared with11.28%，decreased by52.27%，Neutraldetergent fiber content decreased to8.87%compared with67.67%before fermentation，decreased by13.00%，Hemicellulose content decreased to25.48%compared with33.82%，decreased by24.66%，the differences are significant (P<0.05)．Experiment5： Add different concentration of exogenous compound enzymepreparation (mannose：cellulose：xylanase=1：9：90) in culture medium to ferment palmkernel meal at optimized process parameters．Crude protein content and neutral detergentfiber content in the product showed a trend of falling and rising，respectively，and adding alow dose of enzyme (<20mg/g) of crude protein and neutral detergent fiber content hadno significant effect，while adding high dose of enzyme (>20mg/g) had significanteffect．It’s shown that under this fermentation process，compound enzyme should not beadded in the culture medium for solid-state fermentation of palm kernel meal to achievethe best effect of fermentation．Relevant process parameters got from shake-flask fermentation experiment shownthat optimized process parameters of fermenting palm kernel meal in solid state conditionsis that：the best strain combination was＂F2+Saccharomyces cerevisiae＂ at the ratio of1：1；the optimum inoculation was8%；the best addition of bran and ammonium sulfate is20%and4%，respectively；water addition(A)：1.48ml/g，fermentation temperature (B)：35.04℃，fermentation time(C)：7.34d and without sterilization．Compare the variation ofnutrition component before and after ferment under optimized process parameters，then we cansee that solid state fermentation can marked improve the nutrition value of palm kernel meal．...