Effects On The Production Of Enzymes From Microorganisms And Biodegradation By Surfactants

Now, the pollution of municipal and agricultural solid waste becomes more and more serious, and composting is considered as a useful process for the disposal of solid waste. However, there are some problems during the composting, such as the absence of prevailing microorganisms, low efficiency of the biodegradation of the substrate. During the composting, the raw material is transformed through a variety of biological processes in which enzymes play an important role. Enzymes can catalyze the degradation of biomacromolecules, such as starch, protein, cellulose, hemicellulose and lignin. It is obvious that the enhancement of the extracellular enzyme activities will promote the degradation of the biomacromolecules, which will in turn speed up the composting process.Surfactants(nonionic and ionic) are compounds that have both hydrophilic and hydrophobic radicles. Many reports have shown the stimulative effects of surfactants on the production and release of extracellular enzymes, such as cellulose, amylase and protease, in submerged culture or solid state fermentation(SSF). Biosurfactant is a high surface-active agent synthesized by microorganism. Compared with chemical surfactant, biosurfactant has a low toxicity to ecological system of Earth and can be biodegraded by microorganism.The biosurfactant rhamnolipid was produced by Pseudomonas aeruginosa. The product was brownish viscous solid. Finally, HPLC-MS was adopted for the structure identification of the product and the sample was proved to be the mixture of monorhamnolipid and dirhamnolipid.It is a valuable attempt to add surfactant to the composting substrate in order to enhance the enzyme production or activity and promote biodegradation of the substrate, but Composting is a complex biological process that involves myriad kinds of microorganisms and numerous enzymes, so it is hard to investigate the effect of surfactant on microorganisms and enzymes secreted by one microorganism in such a complex process. SSF and composting are quite similar in some characteristics, for example, they are all microbiological transformation within particles of a solid matrix. In this study, we investigated the effects of surfactants on the main extracellular enzymes of Pseudomonas aeruginosa, Bacillus subtilis and Streptomyces badius.The results indicated that Tween-80 at 0.05% significantly increased the production of protease from Pseudomonas aeruginosa and Bacillus subtilis by 65% and 30%. Tween-80 can also significantly increase the production of amylase, protease, xylanase from Streptomyces·badius. Rhamnolipid at 0.018% could promote Bacillus subtilis to produce protease obviously and the activity of protease was increased by 51%. However, rhamnolipid inhibited the production of protease from Pseudomonas aeruginosa. Rhamnolipid at 0.006% could increased the production of protease and xylanase from Streptomyces·badius by 14.6% and 37.6%; But, rhamnolipid at 0.018% inhibited the production of enzymes from Streptomyces·badius. Surfactants influenced the growth of microorganisms, the production of enzymes and biodegradation of organisms obviously, and it has great significance in composting.