[Research progress on plate mixed culture of lignocellulolytic microorganisms].

Mixed culture of microorganisms has been widely used for the research of lignocellulose transformation and degradation, but the results of the mixed culture are largely affected by the interactions of different lignocellulolytic microorganisms. At present, the researches on these interactions are mainly based on plate mixed culture assay. For this assay, two types of plate were used, namely, basic medium plate and improved medium plate. The basic medium plate is mainly used for the study of colony morphology, mycelia color, exocellular volatile organic compounds, and exocellular enzyme activity, whereas the improved medium plate is used for comparative study, with the carbon sources replaced by natural lignocelloses. This paper summarized the present research status and advancement about the plate mixed culture of lignocellulolytic microorganisms, and put forward a prospect about the focuses of future research in this field.

[Microbial community changes during the degradation of straw using phospholipid fatty acid analysis].

Solid-state fermentation system of rice straw was established with the inoculation of soil microorganism and Phanerochaete chrysosporium. Microbial biomass and community structure were investigated using the phospholipid fatty acid (PLFA) technique, and the changes of lignocellulose's degradation rate were also detected during the process. The experimental results show that lignocellulose degradation rate reaches 44% after fermentation. When the total amount of phospholipid fatty acid is separated into indicator phospholipid fatty acids for different groups of microorganisms, these groups show different patterns during the process. Contents of PLFA in gram-positive bacteria, gram-negative and fungi reach their peak value on the sixth day. Gram-positive bacteria have lower contents. The PLFA content ratio of fungi and bacteria is 0.2 - 0.5, so fungi are the main community decomposing lignocellulose. Principal component analysis of the PLFA data show that 18 carbon unsaturated fatty acids are the major fatty acids at the end of the process, which is consistent with the results of indicator phospholipid fatty acids and lignocellulose's degradation rates, so PLFA technique is able to fairly well detect the changes of microbial biomass and community structure in solid-state fermentation system of rice straw.

[Lignin degradation by Penicillium simplicissimum].

A strain of fungi was isolated from soil, which was identified as Penicillium simplicissimum. This strain was capable of utilizing several lignin model compounds, making aromatic dyes decoloration and degrading natural lignin. All these results proved that Penicillium simplicissimum has ligninolytic ability. Three kinds of enzymes were believed to be the most important catalyzes in the biodegrading process. They are lignin peroxidase (LiP), laccase (Lac) and hemicellulase. And they always work synergistically. After 25 days' incubation, the amount of rice straw lignin decreased 0.23g, and the degrading rate was 14.94%. Different from the degrading mechanism of the white-rot fungi, the lignin degradation by P. simplicissimum mainly happened during the primary metabolism and it was greatly influenced by the pH of media, the concentration of Cu2+ and Mn2+.