| Fermenting biogas with rice straw is an immportant way to make progress in biogas industry. However, the lignocellulose in the straw has a complex structure and diffecult to be fermented, which limit their practical application in biomass applications seriously. It is still a great challenge to hydrolyze lignocellulose efficiently for reseachers. There are many studies about lignocellulose degradation, however, some problems, such as the simple component of enzyme system, the low degradation rate or the high fermentation temperature, which made it unsuitable in alpine region. In this study, the sample was collected from the special geography which are rich in decaying vegeta-tion of Hei Longjiang province. A complex bacteria with efficient degradation of lignocellulose was selected at 35 oC by the synergistic effect of the microorganism. the morphological characteris-tics, growth characteristics, acidogenicity and the ability of degradation of lignocellulose was stud-ied. The main contents and results are as follows:1 Selection and construction of composting consortia for degrading lignocelluloseA complex microbial system, named LZF-12, which can degrade rice straw was screened from oil of high cellulose content with rice straw as sole carbon source. Microbial community and deg-radation characteristics are tending towards stability through more than forty subculture. Observed by optical microscope and scanning electron microscope, the micro flora of LZF-12 is complex and microbial morphology is diverse. The system can decompose all the filter paper of flasks in 6 days when it was cultured at 35℃under static condition, and rice straws were softened and basic or-ganization was degraded obviously in 7 days.2 Research on growth characteristicsThe complex microbial system LZF-12 consists of aerobes and facultative anaerobes by ana-lyzing change trends of growth curve and dissolved oxygen curve. Degradation of rice straw de-pends on facultative anaerobes mainly.The system has better buffer capacity to the pH of the envi-ronment and its environmental pH change gave a similar tendency at the conditions of different initial pH.3 Research on fermentation characteristicsIn degrading crude fiber in rice straw, hemicellulose are used by microbial system LZF-12 preferentially,then the cellulose.Lignin is degraded hardly all the way. Till to the end of fermenta- tion,the weight loss of rice straw is up to 66%.VFAs concentration increased and then decreased during fermentation. VFAs concentration came up to the MAX3.44g/L, the sum of acetic acid and butyric acid rose up to 90% of VFAs. It provides suitable substrates for next biogas fermentation.4 Effect of C/N ratio and pretreatment on fermentationIn the text, variations of microbial community concentration,pH,degradation of rice straw and VFAs in fermentation liquor with different C/N ratio are detected,results showed that the lower C/N ratio,the more abundant nitrogen, the degradation of rice straw and VFAs concentration are raised accordingly. Thus,low C/N ratio will be advantageous in degrading rice straw and producing VFAs. Immersion of rice straw with 1%NaOH is an effective and economical pretreatment.5 Mcrobial community dynamics in fermentation by DGGEDGGE analysis showed that microbial species are varied in complex system LZF-12. The dominant consortium are Clostridium sp.,Uncultured Verrucomicrobia and Clostridium cellu-lolyticum. These microbial strains took on high ligincellulose-degrading abilities according to re-lated resources,and they have played an important role in degrading rice straw. Besides,there are some other microbial strains in LZF-12,such as Pseudomonas sp.,Acetivibrio sp.,Uncultured Acidithiobacillus sp. and Uncultured eubacterium.which could use rice straw to produce VFAs in-cluded of acetic acid,butyric acid and formic acid, metabolic pathway of VFAs dominant are formed by these microbial strains... |
PDF Full Text Request