Isolation and evaluation of Lactobacillus brevis from chilli waste for potential use as a wood preservative
D O’Callahan, T Singh, I R McDonald
Lactic acid bacteria were isolated from chilli waste and evaluated for their ability to arrest wood rotting basidiomycetes. In previous work a quick screening method using 96 well plates and measuring absorbance to determine fungal growth was developed specifically to investigate the efficacy of isolated bacteria against wood decay fungi. Using this method, one bacterium (isolate C11) was identified from three bacterial isolates as having significant antifungal properties against Oligoporus placenta. This isolate was identified as Lactobacillus brevis by 16S rRNA gene sequencing and BLAST analysis of the NCBI database. To determine antifungal activity in wood, Pinus radiata blocks were impregnated with L. brevis strain C11 cell free supernatant (CFS) and exposed to brown rot fungi O. placenta, Antrodia xantha, and Coniophora puteana. The CFS treated timber demonstrated resistance to degradation from all fungi especially when L. brevis was incubated for one week before filtering the culture to retrieve the supernatant. To determine the nature of the bacterial metabolites affecting fungal growth, the affect of pH, temperature and proteinaceous enzymes on the CFS was assessed using the 96 well quick screening method. The antifungal metabolites were heat stable and not affected by proteinase K, but were affected by neutralisation with NaOH suggesting the metabolites were of an acidic nature.