| With the continuous expansion of vegetable planting area,the amount of vegetable waste generated has increased significantly.How to handle and dispose these vegetable waste efficiently and safelyhas become a hot research topic in recent years.Aerobic composting as a suitable technical method,which can serve to solve the problem of vegetable wastes in China.However,due to the protective effect of lignin from vegetable wastes and difficult-to-degrade complex structure,these factors have become the speed-limiting conditions for the vegetable wastes composting process.In addition,the high temperature of thermophilic aerobic composting will limit the growth and function of general microorganisms.In order to improve the degradation rate of lignocellulose(lignin,cellulose and hemicellulose)in the vegetable waste composting procecss,enhance the degradation of microorganisms during the high temperature period of the compost,shorten the composting time,and promote the decomposing,the tomato and melon vegetable wastes were selected as the research object to screen out the high-temperature resistant lignin-degrading bacteria,and then studied the degradation potential and the compost maturity effect of these different high-temperature resistant strains on lignocellulose in compost,the characteristics of the lignin-degrading enzymes were also deeply analyzed and the high-temperature resistant lignin degradation bacteria and their degradation mechanism were identified,which could provide an important scientific theoretical basis for the composting of vegetable waste efficiently and safely.The main research results are as follows:(1)8 strains of lignin-degrading bacteria were screened out during the high-temperature composting period of tomato and melon mixed waste by means of screening,purification,and re-screening,all of which had the characteristics of thermostable bacteria.Among them,strain F9 can tolerate high temperature of 50℃ and belongs to heat-resistant bacteria;strains F4,F1 1,F12,F13,Q1 and QK can tolerate high temperature of 55 ℃ and belong to facultative thermophilic bacteria;strain FP4 can tolerate high temperature of 70℃ and belongs to special thermophilic bacteria.These 8 bacteria were identified as Bacillus sp.(2)These 8 heat-resistant strains were then used to carry out the composting experiment of tomato and melon mix waste,and the degradation effect of different heat-resistant strains on lignocellulose in the compost was explored,and the degradation advantage characteristics of each strain were clarified.With the composting time increasing,the degradation rate of lignin and hemicellulose of each strain was fast during the first 7 days,and then tended to be slow,while the degradation rate of cellulose was fast from the 7th to 15th day of composing,followed by the 0th to 7th day,and was extremely slow in the rest time.Comparing the degradation rates of different inoculation treatments,it was found that the absolute degradation rates of lignin and hemicellulose treated with F11 were 14.96%and 11.32%on the 7th day,respectively,accounting for 72.95%and 33.31%of the total degradation of compost(including inoculation bacteria and indigenous).On the 15th day,the lignin degradation effects of FP4,Q1,and QK treatments was the strongest,the contribution rate of these strains was 21.06～25.63%,and the absolute degradation rate and contribution rate of cellulose in FP4 treatment was 9.71%and 17.01%,respectively.On the 31st day,the degradation effects of lignin and cellulose in the strains F11,Q1 and QK treatments were the highest,and their contribution rates were 45.72%～51.14%and 26.31%～31.14%,respectively.It can be seen that the degradation effect of different strains on lignocellulose was significantly different at the different periods of composting,and the highest degradation rate of lignin and hemicellulose mainly occured during the first 7th day of composting,while occurred on the 7th day-15th day for the cellulose.Moreover,the F11,Q1,and QK treatments showed outstanding degradation contribution.(3)In the vegetable waste compost with 8 strains of thermostable bacteria,the change characteristics of lignocellulose degrading enzyme activity under the treatment of different thermostable bacteria were clarified.Lignin peroxidase activity played an important role in degrading lignin during the 7th day～15th day of composting.The enzyme activity of each treatment reached the peak on the 3rd day,with the high value of 15710.87 U/L;The addition of strains promoted the peak time of Manganese peroxidase and Laccase activity,and the peak time was 13 days and 7 days earlier than that of blank control,respectively;Carboxymethyl cellulase and hemicellulose xylanase enzyme activities reached their peaks on the 15th day,with the values of 1793.96 U/g and 6359.12 U/g,respectively.(4)Through high-throughput sequencing technology,the effect of adding bacterial strains on the microbial community in the compost was clarified.The addition of different lignin degrading bacteria made the diversity of bacterial and fungal communities in the pile different.At the 7th day,the Ncardiopsis in F11 and Q1 treatment was significantly higher than that in FP4 and QK treatment 52.54%～198.74%.Bacillus in F11 and Cladosporium in F11 and Q1 treatments were significantly higher than those in other treatments 215.14%～832.80%and 57.97%～97.97%,respectively,which promoted the degradation of lignocellulose.On the 15th day,the Brachybacterium treated with the added strain was 58.70%～99.59%higher than that treated with the control.The relative abundance of Corynebacterium,Aerococcus and Xanthomonadaceae in the compost were significantly lower by 20.95%～71.76%compared with CK treatment.(5)The decomposing effects of vegetable waste was identified under different thermostable bacteria treatments using the outdoor small-scale composting experiment.After 50 days of composting,the organic matter content of the treatments with strains F11,FP4,Q1,and QK was reduced by 6.4%to 8.6%compared with the CK treatment,which promoted the degradation of organic matter.The seed germination index reached more than 50%,which was an increase of 16.57%～37.64%compared with the CK treatment,and the compost basically reached maturity.The F11 treatment promoted the accumulation of nutrients with the maximum total nutrient content was 11.70%,which was 7.93%higher than that of CK treatment.The recommended strains F11,Q1,QK,and FP4 could be served as the dominant strains of lignocellulose degradation in the compost and used for the development and utilization of decomposing inoculants.In summary,8 high-efficiency lignin-degrading strains that can tolorate high temperatures of 50 ℃ were screened out in this study,and their characteristics of degrading lignocellulose were also clarified.Strains F11,Q1,QK,and FP4 are recommended as the advantage stranis for lignocellulose degradation in composing,and the composting maturity effect of these strains was verified,which will provide important data support for the application research and development of the vegetable waste composting compound bacteria for the four strains in the later period,and also provide important theoretical basis for the efficient and safe utilization of vegetable waste. |
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