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[Comparison of two mycelial pellets formation methods to immobilize o-chlorophenol degradation bacteria].

Objective
To find an efficient and fast method for microbial immobilization, we compared simultaneity culture method and adsorption method on morphology and intrastructure of combined mycelial pellets, as well as their o-chlorophenol biodegradation efficiency.


Methods
The o-chlorophenol degrading photosynthetic bacterium PSB-1D was immobilized onto mycelial pellets formed by Phanerochaete chrysosporium DH-1 to form combined mycelial pellets. The morphology and intrastructure of pellets formed by two immobilization methods were observed by optical microscope and scanning electron microscope. Then, their differences were analyzed. Using the sterile medium as control, o-chlorophenol removal efficiency of free photosynthetic bacteria, single mycelial pellets and combined mycelial pellets formed by two methods were studied.


Results
Photosynthetic bacteria were largely concentrated in the core region of pellets formed by simultaneity culture method and grew in clusters on each mycelium and their intersections. As compared with simultaneity culture method, photosynthetic bacteria mainly grew in the transition region of pellets formed by adsorption method. With the same inoculation amount of spores and photosynthetic bacteria, the simultaneity culture method could immobilize more bacteria with little time. Moreover, average diameter, dry weight and dry wet ratio of pellets formed by simultaneity culture method were bigger than that by adsorption method, and their desorption amount were less. The o-chlorophenol degradation followed a first-order kinetics model. The combined mycelial pellets formed by simultaneity culture method could degrade above 89% of o-chlorophenol in medium with an initial concentration of 50 mg/L after incubation for 7 days. And the half-life periods (t1/2) were shortened to 2.8 days.


Conclusion
The study provides the theoretical foundation for the practical application of the new biomass carrier to organic wastewater treatment.