Evaluation of lactic acid bacterium from chilli waste as a potential antifungal agent for wood products

Abstract

Aims: The aim of this study was to isolate lactic acid bacteria from chilli waste and evaluate metabolites produced for the ability to arrest wood decay.

Methods and Results: Using an optical density screening method, one bacterium (isolate C11) was identified as having pronounced antifungal properties against Oligoporus placenta. This isolate was identified as Lactobacillus brevis by 16S rRNA gene sequencing. To determine antifungal activity in wood, Pinus radiata blocks were impregnated with Lact. brevis [C11] cell-free supernatant and exposed to brown rot fungi O. placenta, Antrodia xantha and Coniophora puteana. The treated timber demonstrated resistance to degradation from all fungi. The antifungal metabolites were heat stable and not affected by proteinase K, but were affected by neutralization with NaOH suggesting the metabolites were of an acidic nature. The presence of lactic and acetic acid was confirmed by HPLC analysis.

Conclusions: Lactobacillus brevis [C11] produced acidic metabolites that were able to inhibit the growth of wood decay fungi and subsequent wood decay.

Significance and Impact of the Study: Traditional wood treatments are becoming an environmental issue as the public demands more benign options. The use of lactic acid bacteria which are considered safe for general use is a potential alternative to the conventional heavy metal chemicals currently in use.