Screening of Microorganisms Capable of Biotransforming Certain Monoterpenes Using Substrate Toxicity Test

Monoterpenes, such as Geraniol (G), Geranyl acetate (GA), Citral (CT), Limonene (LN), and Linalool (LL), are the most widely used phytochemicals in the aroma, food, and pharmaceutical industries. Here, we screened several bacteria and fungi to assess their potential to biotransform the selected monoterpenes (G, GA, CT, LN, and LL) through the substrate toxicity test. Three bacteria Pseudomonas fluorescens MTCC2421, Streptococcus mutans MTCC497, and Escherichia coli were found to be resistant to G, GA, and LN while two P. aeruginosa, and S. epidermidis MTTC 435 to GA and LN. In general, all fungal strains did not show resistance to any of the monoterpenes used, except Candida albicans and Fusarium oxysporum, which were slightly resistant to lower concentrations (0.05-0.1%) of GA. Interestingly, none of the bacteria and fungi showed any resistance to CT. The maximum concentrations of monoterpenes to which bacteria exhibited resistance ranged from 0.05-0.2%. The growth and biomass profiles of bacteria revealed that P. fluorescens and S. mutans grew well in the presence of monoterpenes GA and LN. Based on this, Pseudomonas fluorescens was capable of biotransforming GA and LN, while S. mutans only LN. The biotransformation of GA by P. fluorescens produced G and LL on the day 5th and 7th of the incubation. Hence, the study revealed the three potential bacteria, which may be useful in producing new aromatic derivatives from selected monoterpenes through biotransformation.