Metabolite profiling and functional assessment of indigenous Lactobacillus spp. in the fermentation and biopreservation of pathogen exposed tender coconut water using HPLC and GC-MS

Abstract

This study evaluated the fermentation potential and antagonistic activity of four probiotic Lactobacillus strains (L. rhamnosus CWKu-12, L. plantarum CWJ3, L. paracasei CWKu14, and L. casei CWM15) isolated from Cocos nucifera L. var. nana water. Among them, L. plantarum CWJ3 demonstrated the most promising fermentation characteristics, with a stable growth rate and high viable cell productivity. L. plantarum CWJ3 produced elevated levels of lactic acid (7.48 ± 0.98 mg mL−1) and acetic acid (0.18 ± 0.02 mg mL−1) in the fermented coconut water, as quantified by high-performance liquid chromatography (HPLC). Furthermore, all Lactobacillus strains exhibited significant antagonistic activity against Escherichia coli, Klebsiella pneumoniae, and Staphylococcus aureus. After 48 h of combined fermentation, Lactobacillus strains remained viable, while the cell density of the pathogens declined significantly. Volatile metabolite analysis of coconut water samples fermented with combined cultures of Lactobacillus strains and pathogens, using solid-phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS), revealed the production of diverse antimicrobial compounds, including acetic acid, octanoic acid, alcohols, aldehydes, ketones, esters, and phenolic compounds. Acidification, resulting from the production of organic acid, was identified as the primary mechanism of pathogen inhibition. Notably, L. plantarum CWJ3 and L. rhamnosus CWKu-12 produced the highest percentage of volatile acetic acid (13 %–14 % relative peak area), strengthening their antimicrobial effects along with lactic acid. Additionally, all strains effectively reduced polyphenol oxidase activity and controlled enzymatic browning in coconut water. Overall, L. plantarum CWJ3, followed by L. rhamnosus CWKu-12, emerged as strong candidates for food biopreservatives due to their antimicrobial efficacy and antibrowning properties.