Preliminary Study On Thermophilic Bacteria And Moulds In Asparagus Old Stem Compost

Asparagus old stem is a material that different from rice straw and wheat straw, so its microbial community and changes during the fermentation of compost must be different from other straws. It is very necessary to study the microorganisms in asparagus old stem compost in order to attain a kind of high quality mushroom compost. The aim of this work is to isolate and identificate thermophilic bacteria and moulds in asparagus old stem compost, and study metabolic ability and cultivating methods of these strains. This work will improve plenty of data for further developing the decomposing inoculants of asparagus old stem and regulating the composting process.Thermophiles bacteria and moulds in asparagus old stem compost samples were investigated. By dilution-plate method, twenty-two strains of bacteria and twenty-seven strains of moulds were isolated from the samples. According to16S rDNA sequence analysis, preliminary identification of these strains was done. Among twenty-two strains of bacteria, thirteen strains were identified as Bacillus spp., four strains were identified as Pseudoxanthomonas spp., one strain was identified as Paenibacillus sp., one strain was identified as Enterobacter sp., one strain was identified as Brevibacillus sp. and one strain was identified as Paracoccus sp. One strain of bacteria could not be identified because there was no matched gene sequence of bacterial species to be found in the GenBank. By observing the morphological characteristics, among twenty-seven strains of moulds, twenty strains were identified as Penicillium spp., two strains were identified as Monilochaetes spp., two strains were identified as Alternaria spp., one strain was identified as Paecilomyces sp., one strain was identified as Mucor spp., and one strain was identified as Aspergillus sp.The results indicated that Bacillus spp., Pseudoxanthomonas spp. and Penicillium spp. were the most frequently isolated thermophilic microorganisms from the asparagus old stem compost. Through the observation of hydrolyzed circle in CMC plate and filter paper culture method,3strains of bacteria and2strains of moulds were screened from the asparagus old stem compost. By comparing the ratio of hydrolytic circle diameter to colony diameter (D/d)2, strains D-b1and f-24were proved of highly efficient cellulolytic microorganisms. This paper investigated the influence of pH, culture temperature and time on the production of cellulolytic enzymes by strains D-b1and f-24. The results showed that optimal culture conditions for strain Db-1were as follows:initial pH value of6in medium, culture temperature of45℃and culture time of two days, whereas optimal culture conditions for strain f-24were as follows: initial pH value of5, culture temperature of50℃and culture time of five days.This paper screened9strains of thermophilic bacteria and4strains of moulds capable degradation of lignin from asparagus old stem compost samples. The influence of culture time on the production of Manganese peroxidase (MnP) by three strains of moulds was investigated. Results showed that MnP abilities of strains f-2and f-27enzyme increased with the increase of culture time, and reached the maximum values of37.53U/mL and46.5U/mL respectively on the7th day, whereas strain f-19reached its maximum values of MnP abilities (41.15U/mL) on the5th day.