The Screening And Characteristic Study Of Strains With High Tobacco Stalk Degradation Efficiency

In order to solve the problem that the high cost and limited reusing pathways during the utilization of tobacco stalk in tobacco production. The self-making screening medium cotains only tobacco stalk was used to screen microorganisms with tobacco stalk degradation ability. The strains with bigger colony diameter on tobacco stalk medium and some lignin degradation model strains were used to screen strains with high tobacco stalk degradation efficiency. 2 bacteria and 3 fungi were demonstrated have high tobacco stalk degradation efficiency and their enzyme producing characteristics during the degradation of tobacco stalk had been studied. This study will provide some theory foundation and technical support for the biodegradation and high value reusing of tobacco stalk. The main results are as follows:1、 25 bacteria and 13 fungi were screened out from the soil samples with rot ligninocellulose by using tobacco stalk medium as screening medium. 2 bacteria and 1 fungal were selected as tobacco stalk degradation experiment material due to their more than 4 mm colony diameter growing on tobacco stalk medium. The bacteria numbered I was identified as Bacillus megaterium and the bacteria numbered M was identified as Enterobacter ludwigii by using the methods of morphological characterization, 16 S r RNA sequence analysis and fatty acid composition analysis. The fungal strain numbered Z09 was identified as Aspergillus nigers through morphological characterization and ITS sequence analysis.2、The screening of microorganism with nicotine degradation ability was carried out by using screened strains and lignin degradation model strains, simultaneously. The nicotine degradation strains were screened according the standard that the safe nicotine concentration in natural environment no more than 0.05 percentage. The results showed that all the selected microorganisms could degrade the nicotine in tobacco stalk. The nicotine in tobacco stalk was degraded to a safe concentration(500mg/kg) after 15 days fermentation with fungi and 20 days fermentation with bacteria. And the nicotine in tobacco stalk was totally degraded by fungi strain Phanerochaete chrysosporium, Trametes hirsute and bacterium strain Bacillus megaterium after 20 days fermentation.3、The lignin degradation strains were screened from nicotine degradation strains. The results showed that the highest lignin degradation rate reached to 53.75% after 15 days fermentation with Phanerochaete chrysosporium. The highest cellulose degradation rate reached at 28.19% in Trametes hirsute. And the highest hemicellulose degradation rate reached at 24.28% in Phanerochaete chrysosporium. The bacterium strain Enterobacter ludwigii and fungi strain Trametes versicolor showed a better selective degradation of lignin in tobacco stalk.4、The enzyme producing characteristics of microorganisms with high tobacco stalk degradation ability were studied. The fungal strain Trametes versicolor showed the highest laccase enzyme producing ability and the highest laccase enzyme activity was reached at 745.65 U/L. The highest lignin peroxide enzyme activity was detected in Phanerochaete chrysosporium at 88.62 U/L. The bacterium strain Enterobacter ludwigii showed the highest manganese peroxides enzyme activity(103.54 U/L) and cellulase enzyme activity, the highest extra-cellular enzyme, filter enzyme and avicelase activity was reached at 0.78 U/m L, 0.59 U/m L and 0.69 U/m L after 10 days of liquid fermentation. Among all the strains, Phanerochaete chrysosporium showed a relative stable cellulase enzyme activity. Taken together, the fungal strain Phanerochaete chrysosporium showed the best lignin degradation effect and a better enzyme producing ability which means a better application prospect for the biodegradation and reusing of tobacco stalk.