Application Of Enzyme Hydrolyzed Cassava Dregs As A Carbon Source Of Biofloc Technology In Aquaculture

In order to reduce the high cost of biofloc carbon resource and avoid the environment damage from the cassava dregs,the research study the feasibility of appying enzyme hydrolyzed cassava dregs for the carbon resource of biofloc technology.Firstly,we explored the optimum reaction conditions of different enzymes,then,enzyme hydrolyzed cassava dregs,cassava dregs and sucrose was added into the aquaculture tank respectively,finally,we analysed the difference of effect among the three carbon resources through water quality monitoring,and the microbial diversity of biofloc and shrimp intestines were investigated through high-throughput sequencing technology.The results of this study are of great significance to utlize the cassava dregs effeciently,and provide the theoretical references for the mechanism of biofloc technology.(1)The results confirmed that the optimal pH,reaction temperature,enzyme amount,solid-liquid ratio and reaction time of cellulase,saccharifying enzyme,and ?-amylase;(2)The results confirmed that the optimal synergy group,the enzyme amount of cellulase,saccharifying enzyme,and a-amylase was 8000 U/g cassava dregs,4000 U/g cassava dregs and 640 U/g cassava dregs respectively,the reaction time wrer 48h,10h and 40h respectively.It has been improving 97.92%of the reducing sugar concentration by these three kinds of enzyme than a single enzyme,and higher than the theoretical reducing sugar concentration of three.enzymes.(3)The effect of complex function from a variety of enzyme on hydrolysis of cassava dregs.Take the cassava dregs were pretreated and adjusted the ratio of solid to liquid,the main component was glucose reducing sugar,the concentration was 34.75 mg/mL?50.55 mg/mL and 92.32 mg/mL respectively.(4)In the 30 days aquaculture experiment,we built up three types of biofloc systems with three different carbon sources,sucrose(BFT 1),cassava dregs(BFT2)and the cassava dregs of enzymes hydrolysis(BFT3).Water quality were monitored during the whole experiment period constantly,the results showed that the TAN mean concentration and NO2--N mean concentration in BFT3 was 0.19±0.03mg/L and 0.16±0.01mg/L respectively,both were higher than those of BFT1 by 18.75%and 23.08%respectively,and were lower than those of BFT2 by 9.52%and 11.11%respectively;the TSS level and BFV level in BFT3 were higher than other groups,which demonstrated that it is more beneficial to the growth of biofloc by adding the cassava dregs of enzymes hydrolysis.(5)High-throughput sequencing analysis revealed that the relative abundance of heterotrophic bacteria in BFT3 was higher than BFT1 and BFT2 by 20.70%and 1.19%respectively,the relative abundance of probiotics in BFT3 was higher than BFT1 and BFT2 by 11.47%and 61.60%respectively,the percentage of potential pathogenic in top ten dominant microbial communities was lower in intestine sample reared in BFT3(S3)compared to other treatments,It suggested that BFT3 improving heterotrophic bacteria and probiotics in aquaculture environments and inhibiting pathogens to reduce L.vannamei disease by adding the cassava dregs of enzymes hydrolysis.