Properties and mechanism of the antimicrobial peptide APT produced by Lactobacillus ALAC-4

Fungal infection is the huge concerns of crop and food security in the worldwide, promoting the variety of natural antimicrobial agent developments and applications. At present, there has been relatively little research relating to antimicrobial peptide of lactic acid bacteria that inhibits fungi. In this study, the antimicrobial peptide APT produced by Lactobacillus ALAC-4, which was isolated from traditional fermented sour porridge in Inner Mongolia, was focused, and the antimicrobial properties were measured using double-layer plate method. APT performed significant both anti-growth activities against most foodborne microorganisms especially Candida albicans. Candida albicans was used as an indicator strain to detect the antimicrobial activity of APT. The results showed that pores appeared on the cell surface and part of the cell structure remained incomplete, in addition the Candida albicans cell walls were seriously damaged under scanning electron microscope and transmission electron microscope. Concomitantly, soluble total carbohydrate and soluble protein contents increased, and phosphorus consumption, succinate dehydrogenase (SDH) activity and malate dehydrogenase (MDH) activity decreased. It was speculated that APT might contribute towards Candida albicans inhibitions via four potential mechanisms: by damaging cell walls, increasing cell membrane permeability, decreasing phosphonic acid metabolism, and by decreasing the respiratory enzyme activity within Candida albicans.