Study On Biological Degradation Of Water Hyacinth Lignocellulose With White-Rot Fungi And Its Effect On Anaerobic Fermentation

With the increasingly serious problem of eutrophication, water hyacinth and other aquatic plants play an important role in abating nitrogen,phosphorus and other nutritional substances in water bodies and improving water quality, but large number of water hyacinth has brought new environmental problems. if water hyacinth are accumulated, it will lead to secondary pollution, therefore, there is an urgent need for water hyacinth for the utilization of resources. In recent years, wth energy crisis problem increasing, development of biomass energy has become a hot study program of science and technology workers. Due to water hyacinth has higher biogas production potential, anaerobic fermentation of water hyacinth for biogas can not only eliminate the pollution caused by the accumulation of water hyacinth but also provide clean and renewable energy, anaerobic fermentation of water hyacinth for biogas becomes an important technical approach of disposition and utilization, at same time, aquatic plants for water restoration has been caused widespread attention as a new type of biomass materials. The structure and content of water hyacinth lignocelluloses are the bottleneck of the biogas production for water hyacinth. In order to improve the yield of biogas, some measures of pretreatment should be taken to water hyacinth. In this paper the biological degradation technology for water hyacinth lignocelluloses and its effect on the anaerobic fermentation for biogas were studied. An efficient method of improving the biogas production capacity of water hyacinth is attempted to be obtained.Two white-rot fungi-Phanerochaete chrysosporium and Pleurotus ostreatus were inoculated in water hyacinth respectively to investigate the degradation of water hyacinth lignocellulose but also the dyiiamic change of the lignocellulose degradation enzyme activity, glucose content and organic matter content in the progress of the degradation. Results showed that:Both Phanerochaete chrysosporium and Pleurotus ostreatus have a strong ability to degrade lignocellulose in particular for Lignin, after30days’treatment, the degradation rate of lignin, hemicellulose and cellulose which were treated by Phanerochaete chrysosporium were39.42%,16.77%and15.39%respectively while the degradation rate of lignin, hemicellulose and cellulose which were treated by Pleurotus ostreatus were26.92%,14.42%,13.44%respectively; Phanerochaete chrysosporium did not produce laccase in the process of degradation of water hyacinth; the activity of lignin peroxidase and manganese peroxidase reached the higest value in the10d, which were50.12U/g,1.72U/g respectively; For Pleurotus ostreatus, the activity of lignin peroxidase, manganese peroxidase, laccase reached the highest values which were13.77U/g,1.42U/g,64.85U/g in the10d,15d,15d respectively; two white rot fungus both produced cellulase whice have two enzyme production peak in the process of degradation of water hyacinth, cellulase production peak of Phanerochaete chrysosporium occurred in the first10d and25d, the enzyme activity were0.49U/g and0.53U/g,cellulase production peak of Pleurotus ostreatus occurred in the5d and20day, the enzyme activity were0.1U/g and0.09U/g; the trend of two white rot fungi produced hemicellulose degrading enzymes roughly first increased and then downward. the hemicellulase activity of Phanerochaete chrysosporium and Pleurotus ostreatus had reached the highest values in the15d and the10day respectively that were5.13U/g and0.77U/g; The ability of Phanerochaete chrysosporium producing cellulose and hemicellulose were higher than Pleurotus ostreatus. The degradation of lignin by white-rot fungi generally occurs the secondary metabolism stage,at the beginning, the white-rot fungi must provide their own consumption of dissolved organic carbon for growth, so the content of soluble organic matter and sugar were decreased. With the conduct of the process of the degradation, cellulose, hemicelluloses and lignin, the organic matter content was decreased and the content of soluble organic matter was increased.In order to investigate its effect on the anaerobic fermentation of water hyacinth, in this paper, water hyacinth were firstly biologically degraded by two white-rot fungi-Phanerochaete chrysosporium and Pleurotus ostreatus, then put the water hyacinth pretreated by different time to anaerobic fermentation under mesophilic condition(35℃) with total solids (TS) of8%to investigate the anaerobic fermentation characteristics of water hyacinth. The results show that the biogas production capacity of water hyacinth pretreated by Phanerochaete chrysosporium or Pleurotus ostreatus for10days or15days are improved with gas production (ml)/TS (g) improved by48.73%～75.05%, gas production is significantly negatively correlated with cellulose content and hemicellulose content; due to the increased gas production, methane production is increased,with methane production(ml)/TS (g) increased by30.53%～55.81%and the biogas production and methane production of water hyacinth which have been degraded by Phanerochaete chrysosporium or Pleurotus ostreatus by25days are reduced. Get all these results together we can make a conclusion:biological pretreatment of water hyacinth lignocellulose by Phanerochaete chrysosporium or Pleurotus ostreatus for appropriate time can significantly improve the biogas production and methane production of anaerobic fermentation of water hyacinth.