Preparation and application of bacteriophage-loaded chitosan microspheres for controlling Lactobacillus plantarum contamination in bioethanol fermentation

Bioethanol fermentation performed by Saccharomyces cerevisiae is often inhibited by bacterial contamination, especially lactic acid bacteria (LAB). Bacteriophages with high specificity can efficiently control bacterial contamination. In this study, Lactobacillus plantarum bacteriophage was embedded into chitosan using a membrane emulsification method and used to control L. plantarum contamination in bioethanol fermentation. The prepared bacteriophage-loaded chitosan microspheres were characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The size homogenization of the prepared microspheres was realized through a fast membrane emulsification device with a Shirasu porous glass (SPG) membrane tube, and the diameter of the homogenized microspheres was about 30 μm. The small d value ( i.e. , 2.015) indicated the narrow range of the size distribution. Swelling experiments indicated that the bacteriophage was successfully enwrapped in chitosan microspheres. To mimic the bacterial contamination in industrial bioethanol fermentation, L. plantarum American type culture collection (ATCC) 8014 was co-cultivated with S. cerevisiae CEC B9S-15 in yeast extract peptone dextrose (YPD) broth. Bacteriophage-loaded chitosan microspheres were added into the simulated contaminative fermentation system to evaluate the controlling effect on L. plantarum contamination by releasing bacteriophages. Compared with the contamination group, the final ethanol content of the bacteriophage-loaded chitosan microspheres treatment group increased obviously ( P < 0.01). It indicated that L. plantarum contamination could be effectively controlled by bacteriophage-loaded chitosan microspheres. The bacteriophage-loaded chitosan microspheres can effectively control L. plantarum contamination in bioethanol fermentation. Moreover, sustained release of bacteriophage would enhance the effect of bacteriophage through prolonging the action time.