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| Screening, Lignocellulose Enzyme Activities and Gene Expression Analysis of Saprophytic Fungi for Decomposing Bamboo Sawdust |
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Abstract The purpose of this research was to screen high efficient decomposing fungi for practical applications to accelerate the decay of moso bamboo (Phyllostachys edulis) stump, and analyze the changes of lignocellulose enzyme activities and gene expression during the decomposing of bamboo sawdust. Lignocellulose enzyme activity were detected primary on the plates containing congo red, aniline blue, and guaiacol for the 61 fungi strains isolated from soil of bamboo plantation (P. violascens). The results showed that 5 fungi strains (P17, P26, P68, P69 and P73) represented significantly higher lignocellulose enzyme activity. Three saprophytic fungi strains of them (P17, P26 and P69), which hold the higher efficiency to degrade the bamboo sawdust in terms of mass loss rate, were tested for their enzyme activities of lignin (laccase (Lac), lignin peroxidase (Lip)) and cellulose (endoglucanase(EG), cellobiohydrolase(CBH)), and gene expression of lignocellulose (cbhⅠ, laccase-like multicopper oxidase gene (lcc)). Based on morphological characteristics and sequence alignment analysis of rDNA-ITS region, the 3 fungi strains were Trichoderma virens, T. asperellum and Mucor racemosus for stains P69, P26, and P17, respectively. The mass loss rate of bamboo sawdust caused by T. virens, T. asperellum and M. racemosus were 20.56%, 17.66% and 13.11% after 20 days decomposition, respectively. The activities of CBH and Lip reached its peak on the 12th day during the decomposition, while Lac activity reached its peak on the 9th day for all the three fungi. The highest of the activities for EG, CBH, Lac and Lip were detected always in T. virens when the activities of 4 enzymes reached their peaks of the three fungi. The analysis of fluorescence quantitative PCR (qPCR) showed that the cbhⅠ gene expression number in T. virens (1.93×105~8.76×106 per microgram of RNA) was significantly higher than those in T. asperellum (1.29×104~4.64×105 per microgram of RNA) and M. racemosus (2.42×104~7.8×105 per microgram of RNA) at all points of observation. The expression number of lcc gene in T. asperellum (9.23×105~4.89×106 per microgram of RNA) was also significantly higher than that in T. asperellum (3.74×105~9.36×105 per microgram of RNA) and M. racemosus (8.91×104~8.16×105 per microgram of RNA) at all points of observation. The results of Pearson's correlation coefficient (r) analysis showed that Lac activity secreting by the 3 fungi was positively correlated with the mass loss rate of bamboo sawdust during decomposition. At the same time, there was a certain synergy between EG and CBH of the 3 fungi stains. However, EG activities secreting by M. racemosus was positively correlated with the mass loss rate of bamboo sawdust, which be differ from the other 2 stains, suggesting there are differences in species characteristics of fungi during decomposing bamboo sawdust. Moreover, the expression of cbhⅠ gene showed a positive correlation with CBH activity of the three fungi during decomposing bamboo sawdust. These results indicated the capacity of decomposing bamboo sawdust for the three saprophytic fungi from higher to lower was as follows: T. virens, T. asperellum and M. racemosus, and Lac played an important role during the decomposing process.
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Received: 29 April 2016
Published: 01 October 2016
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| Fund:National Natural Science Foundation of China |
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