Screening of the Strains for Food Waste Fermentation and Production of Aquatic Compound Feed
|Course||Aquatic Products Processing and Storage Engineering|
|Keywords||food waste strains fermentation aquatic feed HACCP|
Food waste(FW) had been a big part of solid waste in city. It had already been a serious problem, because of its easily spoilage, and food safety of“protein homologous”by direct use as feed livestock, as well as its big population in city waste. It should be urgently solved how to dispose for urban environment protection. In order to explore the processing of FW, superior strains were screened from FW in this paper, then FW, rich in nutrition, was fermented as substrate by inoculating strains obtained. For the purpose of improving the protein content of fermentation substrate, a series of experiments including initial and repeated screening were conducted and the fermentation conditions were also optimized to change the nutrition structure of FW, so that it can be used as material of livestock feed and aquatic feed.To investigate the fermentation effect of single strains on FW, three strains obtained from FW and named L22、Lc、Ydy, respectively, was inoculated singly in FW combined with the strain of S1, which preserved in our laboratory. Results showed that Lc and L22 were lactic acid bacteria, Ydy was yeast and S1 was amylase-producing bacteria, respectively. A good fermented flavor occurred by inoculating with Lc, L22, and Ydy. The growth of E.coli was effectively inhibited by Lc and the T-VBN content of FW was only 4.37mg/100g after 36 hours fermentation with Lc. It demonstrated that these strains are benefit to preserve the FW. The second was Ydy and L22. S1 has no influence on the growth of E.coli and the T-VBN content of FW reached 13.81mg/100g after 36 hours, which was still within the limitation of freshness. The true protein of the fermentation groups inoculated with Lc, Ydy were increased by 64.89% and 23.63%, respectively, but the changes of true protein content with L22 and S1 were not obvious. Glucose, derived from the decomposition of starch by S1, can be used as carbon source of the growth for Lc, Ydy and L22. The function of Lc was better than that of L22, so a mixture of Lc, Ydy and S1 can be used as a fermented for FW fermentation.To investigate the influence of inoculate conditions on the growth of Lc and Ydy, single factor experiments were carried out. Results shows the optimization condition of Lc was that: 30℃, initial pH value was 6.0, volume of liquid was 130/250mL, and fermentation time was 36h; additionally, the optimization condition for Ydy was that:30℃, initial pH value is 5.5, volume of liquid was 130/250mL, and fermentation time was 24-36h.Lc and Ydy were identified with the method of 16S rRNA and 18S rRNA and results showed that Lc was Lactococcus lactis and Ydy was Candida tropicalis.FW was fermented by three-combined strains. Mixture ratio of these strains, inoculums concentration, fermentation time, coupled with the initial pH value were investigated by single factor experiment and orthogonal L9(34) test in this paper. Results showed that the optimal fermentation condition were as follows, mixture ratio of strains (Lc:Ydy:S1) of 3:2:1 and 0.15% inoculum concentration under the initial pH value of 5.0 for 48 hours fermentation. Furthermore, expanding experiment indicated that the quality of food waste was improved by fermentation under the optimal fermentation condition. The content of true protein had increased by 45.8% from 15.42% to 22.47%. The population of E.coli had decreased to 30cfu/g after fermentation; the population of Lactobacillus and Yeast were 1.5×10~9 cfu/g and 6.6×10~8 cfu/g, respectively.For the purpose of achieveing industrial production of FW fermentation, pilots test was carried out in Lvhuan biotechnology Co., Ltd, Zhoushan, Zhejiang province. Results showed that it needed to add accessories(bran and corn flour) with 30% of fermentation substance and expand inoculums concentration to 20% at the condition of water content with 65%. The optimization fermentation temprature was 30℃for 24 to 48h. To evaluate the vendibility of the fermentation feed, cost accounting was analysised in this paper and showed that the price of fermentation protein feed was 1620 yuan per ton that had a strong competitive advantage. Besides, the fermentation protein feed instead of fish meal was used as a material for preparing aquatic feed with the method of linear programming. The price of compound feed, made by fermentation protein feed, was lower than that made by fish meal.The application of HACCP on fermentation protein feed production was explored because of the safety problems of food waste. After having an actual inspect on Lvhuan biotechnology Co., Ltd, three critical control point including cleaning and sterilizing the corner of the machine, mental detection and measurement package were made sure.