Effect of combination of Oxyrase and sodium thioglycolate on growth of Clostridium perfringens from spores under aerobic incubation

Inactivation of Clostridium perfringens C1 Spores by the Combination of Mild Heat and Lactic Acid

Clostridium perfringens is a major pathogen causing foodborne illnesses. In this experiment, the inactivation effects of heat and lactic acid (LA) treatments on C. perfringens spores was investigated. Heat treatment (80 °C, 90 °C and 100 °C), LA (0.5% and 1%), and combined LA and heat treatments for 30 and 60 min were performed. Residual spore counts showed that the count of C. perfringens spores was below the detection limit within 30 min of treatment with 1% LA and heat treatment at 90 °C. Scanning electron microscopy and confocal scanning laser microscopy results showed that the surface morphology of the spores was severely disrupted by the co-treatment. The particle size of the spores was reduced to 202 nm and the zeta potential to −3.66 mv. The inner core of the spores was disrupted and the co-treatment resulted in the release of 77% of the nuclear contents 2,6-pyridinedicarboxylic acid. In addition, the hydrophobicity of spores was as low as 11% after co-treatment with LA relative to the control, indicating that the outer layer of spores was severely disrupted. Thus, synergistic heating and LA treatment were effective in inactivating C. perfringens spores.

Microbial community dynamics during alfalfa silage with or without clostridial fermentation

This study was conducted to examine the effects of Lactobacillus plantarum (LP) and sucrose (S) on clostridial community dynamics and correlation between clostridia and other bacteria in alfalfa silage during ensiling. Fresh alfalfa was directly ensiled without (CK) or with additives (LP, S, LP + S) for 7, 14, 28 and 56 days. Clostridial and bacterial communities were evaluated by next-generation sequencing. Severe clostridial fermentation occurred in CK, as evidenced by the high contents of butyric acid, ammonia nitrogen, and clostridia counts, whereas all additives, particularly LP + S, decreased silage pH and restrained clostridial fermentation. Clostridium perfringens and Clostridium butyricum might act as the main initiators of clostridial fermentation, with Clostridium tyrobutyricum functioning as the promoters of fermentation until the end of ensiling. Clostridium tyrobutyricum (33.5 to 98.0%) dominated the clostridial community in CK from 14 to 56 days, whereas it was below 17.7% in LP + S. Clostridium was negatively correlated with the genus Lactobacillus, but positively correlated with the genera Enterococcus, Lactococcus and Leuconostoc. Insufficient acidification promoted the vigorous growth of C. tyrobutyricum of silage in later stages, which was mainly responsible for the clostridial fermentation of alfalfa silage.