| Lees are a major by-product of the brewing process in solid Baijiu production and are also a major contaminant.The lees are rich in nutrients and are an excellent source of organic fertiliser.However,lees are highly acidic and perishable,and large quantities of lees can pollute the environment and cause significant waste if not disposed of in a timely manner.In line with the idea of circular economy and sustainable development,the preparation of bio-organic fertilizers from screened functional microorganisms is of great significance for the utilization of wine lees.In this study,the soil of a sorghum plantation in a Guizhou-based liquor company was used as the screening material for the targeted screening of nitrogen fixing and phosphorus solubilizing strains,and was identified morphologically and molecularly.The soil was also used to screen two strains of phosphorus solubilising bacteria,and the growth curves of the phosphorus solubilising strains were plotted to observe their growth characteristics.The phosphorus solubilisation characteristics of the monocultures and mixed cultures were then investigated using temperature,p H and inoculum as single variables,and water-soluble phosphorus content was determined using an enzyme standard.The organic acid content in the fermentation broth of phosphorus-dissolving bacteria was determined by high performance liquid chromatography,and qualitative and quantitative analysis was performed.Finally,the organic fertilizer was prepared by fermenting the lees with the cellulolytic bacteria strains screened in the laboratory,and the organoleptic and physicochemical indexes were measured during the composting process.The main research results are as follows:1.Using the soil of a sorghum planting site of a soy sauce Baijiu enterprise in Guizhou as the sample,two strains of highly efficient phosphorus-dissolving bacteria P1 and P2 and one strain of nitrogen-fixing bacteria N1 were successfully isolated through selective medium directed screening,and were initially identified by morphology and molecular biology as Enterobacter ludwigii and Pantoea The strains were initially identified as Enterobacter ludwigii and Pantoea dispersa,and Azotobacter chroococcum.2.The phosphorus solubilisation performance of the two strains was measured and the SI values of phosphorus solubilisation index of strains P1 and P2 were 1.63 and 2.45 respectively,with the SI value of strain P2 being higher than that of the currently reported phosphorus solubilising bacteria,indicating that strain P2 was able to degrade inorganic phosphorus efficiently.The two strains of phosphorus solubilizing bacteria were also measured to have certain degradation ability for insoluble phosphorus at 30 ℃ and 180 r/min,and the phosphorus solubilization amount of mixed bacteria culture was better than that of monoculture at this condition,which could reach 2.49 times.The p H of the fermentation broth showed an increase from 4 to 5 and then to 8 in the early stage,and the number of viable bacteria increased and then decreased in the process of both monoculture and mixed culture.3.The growth curves of P1 and P2 strains in liquid culture showed that the growth rate of P1 was higher than that of P2.Different conditions had certain effects on the phosphorus removal of the strains,among which,P1 bacteria reached the maximum phosphorus removal of 308.41 mg/L at p H=5,and the degradation rate was30.84% respectively;P2 bacteria and mixed bacteria culture at 40 ℃ reached the maximum phosphorus removal of 287.11 mg/L and 338.21 mg/L respectively,and the degradation rate was 28.71% and 33.82% respectively.2 strains The maximum inorganic phosphorus solubilization amount of strain 2 was higher than most of the phosphorus solubilizing strains reported in the past three years,which was about1.2-17.1 times higher,indicating that strain 2 had excellent inorganic phosphorus degradation ability.4.The organic acids in the fermentation broth of strains P1 and P2 were qualitatively and quantitatively analysed by high performance liquid chromatography.In the fermentation of P1 and P2 bacteria,acetic and oxalic acids were mainly produced in the fermentation broth with the maximum amount of 4103.65 mg/L.P2 bacteria mainly produced acetic and succinic acids with the maximum amounts of468.55 mg/L and 528.60 mg/L,respectively.in the mixed fermentation of P1 and P2 bacteria,acetic and oxalic acids were mainly produced with the maximum amounts of761.46 mg/L and The moisture content of both lees was around 50%,while the starch and protein content of lees A was 15.26% and 9.91% respectively,while that of lees B was 10.51% and 7.95% respectively.The lower p H and germination index of both lees indicated that the lees were acidic.During the accumulation of both lees,the organoleptic appearance changed from a brown,hard and heavy substance at the beginning and a distinct lees odour to a black,loose substance,lighter weight and no distinct odour at the end.78.16% and 83.92%,respectively.The tr germination index,compared to the organic fertiliser of treatment group 1,was 7.99 and 6.53 times higher,respectively.The nitrogen content,organic matter,germination rate and germination index of treatment group 2 and plant organic fertilizers were significantly higher than those of plant organic fertilizers,especially the germination index,which was 7.99 and 6.53 times higher,respectively.5.Bio-organic fertilisers were prepared by adding functional bacterial agents to the two types of lees organic fertilisers.Through the determination of relevant physicochemical indicators,moisture,p H,organic matter and effective live bacteria count were all within the qualified range,especially the organic matter content was high,reaching over 60%.Meanwhile,the test on the effect of bio-organic fertilisers on seeds showed that the germination rate of the 2 bio-organic fertilisers was greater than 95% and the germination index was greater than 80%,indicating that the germination index of the formulated bio-organic fertilisers reached a good level and could achieve no harm to the growth of crops. |
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