Research On Characteristics Of Ligninolytic Microorganisms And Their Effect On The Humification Of The Agricultural Wastes Composting

Agricultural wastes, especially crop straws, contain many quantities of lignocellulose. The main component, lignin, is difficult to be biodegraded due to the complex component and leads the insufficent transfomation of humus and low quality of compost. So accelerelating the humification of lignin is critical to the sufficient maturity of the agricultural wastes. Characteristics of ligninolytic microorganisms and their effects on the humification of the agricultural wastes composting were studied. Firstly, the lignin degrading characteristics of Penicillium simplicissimum, Streptomyces badius and one composite microorganism were studied. Based on these, the effect of biodelignification of rice straw by different ligninolytic organisms on humus formation was discussed in solid state fermentation. Lastly, the lignocellulolytic microorganism, Phanerochaete chrysosporium, was inoculated during different phases of agricultural wastes composting and its effects on the humification were studied. These results would give theory instruction for accelerating composting and improve the compost quality.The laccase activities of P. simplicissimum during solid state fermentation with rice straw were studied. Results showed that all supplemental carbon nutrients inhibited the laccase activity, while proper concentration of supplemental nitrogen sources remarkably enhanced the laccase activity. The enhancement of laccase activity by ordinary laccase inducers 2, 2'-azino-bis (3-ethylbenzthiazoline-6- sulfonic acid) and xylidine was not observed in this study. Lignocellulose degradation was improved when laccase activity was relatively low during the fermentation, which proved the polymerizing and depolymerizing function of laccase in lignin degradation by P. simplicissimum. All supplemental sources might induce the peak of Lac activity on day 3 when the polymerizing function was especially strong.The lignocellulose degradation of rice straw by Streptomyces badius during solid state fermentation was researched. The results showed that nitrogen resouce-yeast extract stimulated the production of peroxidase and increased the degradation rate of lignin. However they inhibited the production of both hemicellulase and cellulase. They also decreased the degradation rate of the hemicellulose and cellulose. Nitrogen source-yeast extract obviously stimulated the production of APPL, but nitrogen source-ammonium chloride and carbon source-glucose inhibited its production. Three composite microorganisms (MC1, MC2 and MC3) with the ability of lignin degradation were screened from three stages of agricultural waste composting and the three stages were warming phase, cooling phase and falling phase, respectively. The results of preliminary screening and further screening both indicated that the composite microorganism MC1 screened from the warming phase had the best ability to degrade lignin. And then, orthogonal experiment was adopted to study its nutritional regulation. The results showed that the optimum integrative culture conditions of MC1 were as follows: rotate speed was 120 r/min; the first carbon source was sucrose, nitrogen source was peptone. ATBS, Veratryl alcohol, Tween-80, Cu2+ and Mn2+ should be added and the second carbon source was added after 2 days. Undering the optimum integrative culture conditions, the enzyme activity of LiP, MnP and Lac after 6 days were 579.91 U/L, 882.49 U/L and 80.94 U/L, respectively. The lignin degradation rate was 46.75% after 10 days.The effects of biodelignification of rice straw by two different ligninolytic organisms (P. chrysosporium and S. badius) and aboriginal microbe on humus formation were compared. The results indicate that lignin degrading microorganisms could promote humus formation. Furthermore, S. badius could accelerate the humus formation more than P. chrysosporium. Since the degrading mechanisms of two strains were different, the approaches of humus formation from lignin with P. chrysosporium and S. badius were also different. P. chrysosporium metabolized lignin to simple molecules (FA), which then were polymerized to complex molecules (HA). While S. badius modified lignin to HA, which then were transformed to FA.The lignocellulolytic microorganism, P. chrysosporium, was inoculated during diifferent fermentation phases of agricultural wastes composting and its effects on humus, compost maturity and spectroscopic characterization of humic acid fraction were investigated. The results showed that it has no obvious effect on the lignin degradation and humus formation when P. chrysosporium was inoculated during the first fermentation phase of composting, but it can increase the lignin degradation and stimulate the humus release when it was inoculated during the second fermentation phase of composting. When inoculated during the second fermentation phase, P. chrysosporium shorten the period of the composting, while it did not short the period of the composting when inoculated during the first fermentation phase. Spectroscopic characterization of humic acid fraction showed that the inoculation P. chrysosporium increased the degree of the aromatization and the molecular polymerization of humic acid when inoculated during second fermentation phase, while it did not produce an obvious change on the humification degree of humic acid when inoculated during the first fermentation phase.