Quality Evaluation Of Aerobic Fermentation Products Of Kitchen Waste And Its Application In The Diet For Carassius Auratus

In this study,two strains CY-1 and CY-7 with strong decomposition ability were identified from kitchen waste and activated sludge as tested strains by BHI and LB medium culture and plate screening of protease,lipase and amylase.The fermentation conditions of single strain and mixed fermentation were optimized and determined,and the solid-state fermentation agent was made with enzymes.The aerobic fermentation of kitchen waste was carried out in BYM-F1-2 kitchen waste machine for 25 d,the optimum fermentation agent was determined,and the fermentation products of kitchen waste（FPKW）were obtained from the BYM-F1-10 kitchen waste machine.The physical properties,nutrient composition,trace elements,harmful microorganisms and toxins of FPKW were systematically evaluated.A-60d-feeding trial was conducted to evaluate effects of dietary different supplement of FPKW（0%,3%,6%,9%,12%,15%and30%,equal nitrogen）on growth performance,apparent digestibility,blood biochemical indexes and digestive enzymes of carassius auratus with initial body weight of7.40±0.21g.The result showed that:1.A total of 8 bacterial strains were screened from kitchen waste and activated sludge,and the strains with high activity of CY-1 and CY-7 were finally obtained by plate screening of protein,lipase and amylase.The colony formed by CY-1 strain was round,larger,gram-positive bacteria,non-anaerobic growth,its 16S rDNA was sequenced with1491 bp,the homologous confidence degree of Bacillus Velezensis in the evolutionary tree analysis reached 71,and the CY-1 strain was judged to be Bacillus Velezensis;CY-7 strain was small colonies,round,moist,light yellow,gram-negative bacteria and not anaerobic growth,its 16S rDNA was sequenced with 1480 bp,the homologous confidence degree of Acinetobacter calcoaceticus in the evolutionary tree analysis reached 100,and the CY-7strain was judged to be Acinetobacter calcoaceticus.2.The strain CY-1 and strain CY-7 were cultured by single bacteria and mixed bacteria（1:1）,it was found that the total number of mixed cultures of CY-1 and CY-7（9.1×10⁸ cfu/g）strains was higher than that of CY-1（5.3×10⁷ cfu/g）or CY-7（3.5×10⁷cfu/g）.The strain CY-1 and strain CY-7 were selected to mix and ferment in 7L fermentation tanks,values of OD660 showed that the lag phase of mixed fermentation of CY-1 and CY-7 was about 4 hours,then entered the log phase,and entered the stationary phase in about 20 hours;the enzyme activity of two strains reached a stable period around16 h of fermentation（protease 47.2 U/ml,lipase 20.9 U/ml,amylase 38.9 U/ml）;After fermentation to 16 h,spores began to appear,and when fermented to 20 h continuously,the spore formation rate reached more than 90%and began to produce a large number of spores.3.Addition of enzyme and solid bacterial agent in BYM-F1-2 kitchen Waste Machine,after 25 d fermentation can reach 94.23%weight reduction rate,the total number of bacteria in the fermentation process can reach 10¹11 cfu/g,fermentation conditions of enzyme and solid bacterial agent were selected and fermented continuously for 25 days in BYM-B1-10 bio-kitchen waste machine,and the FPKW were obtained for follow-up test.4.Uncrushed FPKW is brown solid,after being filtered by grading sieve,weight ratios of the residues（mainly bone and fiber）on 8 mesh,12 mesh,20 mesh,32 mesh were35.94%,22.92%,22.12%and 11.98%respectively.In comparison,FPKW through a 32-mesh sieve was a fleshy yellow powder,and the weight ratio of FPKW was 7.85%.The content of crude protein,crude fat,ash,and moisture of FPKW was 18.7%,20.4%,5.7%,7.5%respectively.In FPKW,the total content of amino acids was 17.43%（EAA 7.1%）,and glutamic acid content highest 2.68%,lysine 1.09%,methionine 0.37%;total phosphorus 1.18%,water-soluble chloride 1.65%;magnesium 990mg/kg,iron 240mg/kg,copper 5.5mg/kg,zinc 39 mg/kg,selenium 0.62 mg/kg,arsenic 0.089mg/kg respectively,and lead,mercury,cadmium and chromium not detected;residual fermentation products contained 17 kinds of amino acids,the total content was 17.43%,essential amino acids was7.1%,accounting for 40.73%of total amino acids,glutamic was the highest（2.68%）,lysine 1.09%,methionine 0.37%.According to the evaluation of AAS and CS,the first limiting amino acid of FPKW was Valvaline.5.No aflatoxins,vomitoxins,Salmonella and coliforms were detected in 0 d FPKW.The content of aflatoxin B1 in FPKW was 9.36 ug/kg after 10 days’open-bag storage at room temperature.In comparison,the content of aflatoxin B1 in FPKW was 13.55 ug/kg after 10 days’sealed storage at room temperature in plastic bag lower than the national feed raw material limit standard also.In either case,vomit toxins,salmonella and coliform bacteria were not detected from FPKW.6.（1）When the dietary supplementation of FPKW was 9%,the weight gain rate（WGR）of Carassius auratus was significantly higher than that of the control group and other treatment groups（P<0.05）.When the dietary supplementation of FPKW reached30%,the WGR of Carassius auratus was significantly lowest among all groups（P<0.05）.The relationship between WGR of Carassius auratus（Y）and the dietary supplement of FPKW（X）could be expressed as Y=-1579.8X²+364.47X+282.02（R²=0.7313）.According to the quadratic regression equation,when dietary optimum supplementation of FPKW was11.5%,WGR_max of Carassius auratus could be obtained;the optimal range of FPKW in aquafeed was 1.7%²1.3%;（2）When the dietary supplementation of FPKW less than 15%,Carassius auratus were no significant difference in the apparent digestibility of dry matter and crude protein in the feed.The trypsin activity in the midgut and hepatopancreas of Carassius auratus showed a trend of first increasing and then decreasing with the proportion increase of FPKW.When supplementation reached 30%,the protease activities in the midgut and liver decreased significantly（P<0.05）;The lipase activities in the hepatopancreas and midgut of Carassius auratus both reached peak（32.49U/mg prot,52.01U/mg prot）;The amylase activity of Carassius auratus decreased with the supplementation of FPKW among all treatment groups.（3）The content of serum glutamate transaminase,glutamate transaminase,alkaline phosphatase,SOD,T-AOC and lipids in Carassius auratus increased with the increase of the proportion of FPKW added.Tissue sections of Carassius auratus confirmed that the intestine,liver and kidney of juvenile Carassius auratus were damaged to a certain extent in the high FPKW supplementation group.The above results show that the mixed fermentation fungus liquid of strain CY-1 and CY-7 can deal with the kitchen waste efficiently in the kitchen waste machine,and can greatly reduce the risk of harmful microorganisms and toxins,and the nutritional index of the fermentation products of kitchen waste conforms to the nutritional standard of feed raw materials.The addition of appropriate amount in Carassius auratus feed can promote the growth of Carassius auratus after crushing and sieving treatment,and there was no significant effect on the weight gain,apparent digestibility and digestive enzyme activity of Carassius auratus when the amount of addition was not more than 15%.