Inhibitory effect of licorice extract on the germination and outgrowth of Paraclostridium bifermentans spores

Abstract

IntroductionParaclostridium bifermentans is responsible for spoilage properties in vacuum-packaged meat. Ordinary heat treatment techniques are ineffective to control the extremely heat-resistant spores of P. bifermentans. Therefore, finding a new strategy to prevent the contamination of P. bifermentans spores in vacuum-packaged meat is challenging.MethodsIn this study, P. bifermentans was isolated from the vacuum-packaged chicken, and the inhibitory effects of licorice extract on the germination and outgrowth of P. bifermentans spores, as well as the key bioactive components in the licorice extract involved in inhibiting spore activity, were investigated.ResultsThe spores induced by combination-nutrient-germinant (150 mmol/L L-alanine and 20 mmol/L inosine, co-AI) did not germinate when the concentration of licorice extract was ≥ 3.13 mg/ml. The germination of P. bifermentans spores induced by non-nutrient-germinant (8 mmol/L dipicolinic acid, DPA) was completely prevented by licorice extract at least 1.56 mg/ml. While the outgrowth of P. bifermentans spores was inhibited at a concentration of 0.39 mg/ml. Licorice extract did not seem to damage the non-germinated spores but blocked the germinant sensing. Licorice extract prevented the outgrowing spores from becoming vegetable cells by disrupting the inner membrane. Furthermore, the results obtained from LC-MS data analysis exhibited 15 key bioactive compounds in licorice extract, such as glycyrrhizic acid, liquiritin, etc. Among them, glycyrrhizic acid and liquiritin apioside exerted efficient inhibitory properties on the germination and outgrowth of P. bifermentans spores.DiscussionThis present study demonstrated that licorice extract can be used as a promising inhibitor of spores and provides a new method to control the residual P. bifermentans spores in meat products. Meanwhile, this study exhibits a baseline for the better understanding of the potential application of licorice extracts to control the P. bifermentans spores in meat products.

Effects of rearing systems (cage versus floor) on the microbial composition and transcriptome of goose ileum

“…Some species of Paraclostridium have been linked to fatal infections in humans and animals ( 72 ), but the mechanism is unknown ( 73 ). It was certain that Paraclostridium was associated with poultry meat spoilage and was difficult to eradicate ( 74 ). Succinivibrio , belonging to the family Succinivibrionaceae , ferments glucose and other carbohydrates to produce large amounts of acetic acid and succinic acid ( 75 ), which might have pro-inflammatory effects ( 76 ).…”

Inactivation Effect of Germination Combined with Cold Plasma Treatment on Bacillus licheniformis Spores

“…The optical density at 600 nm (OD 600 ) gradually dropped by up to 60% during germination [18]. The decrease in OD 600 can be used for evaluating spore germination.…”

“…Spore suspensions, both before and after treatments, were adjusted to a concentration of 10 6 CFU/mL and fixed on sterile slides. The slides were then stained with membraneimpermeable staining pyridinium iodide dyes (PI, 3 µL in 1 mL, Invitrogen Trading Co., Ltd., Shanghai, China) and stored in the dark at room temperature for 45 min [18]. The fluorescence emitted by the stained samples was observed using a CLSM with a 63 × oil immersion objective (TCS SP8, Leica Microsystems, Wetzlar, China), utilizing an excitation wavelength of 490 nm and an emission wavelength of 635 nm.…”

“…It has been reported that after entering the germination stage, spores gradually lose their heat resistance [8]. Therefore, a certain level of heat treatment (80 • C, 20 min) can only kill vegetative cells, allowing for the enumeration of surviving spores [18]. In Figure 3A, the number of surviving B. licheniformis vegetative cells was significantly lower (p < 0.05) in Ar compared to air; however, there was no significant difference (p > 0.05) in spore viability.…”

“…Therefore, there is a growing interest in finding ways to inactivate spores while also improving the sensory qualities of processed foods. Compared to conventional heat treatment, a more efficient approach is to promptly inactivate spores once germination occurs [18]. Several studies have demonstrated the effectiveness of emerging and alternative methods such as pressure-assisted thermal sterilization [19], high-pressure carbon dioxide [20], supercritical fluid carbon dioxide [21], and cold plasma treatment for food sterilization [22].…”