Isolation and screening of D-limonene-resistant microorganisms

This study reports the isolation of microorganisms that are resistant to environment containing limonene, the most important residue in the citrus industry. For the isolation, samples collected from strategic places of a citrus processing plant ( yellow water, entrance and exit of the bagasse tank, effluent and deteriorated fruits found in bins, machine straps, fruit washers and plant floor), some citrus fruit and mint from local market were used. The samples were incubated in rotary shaker at 30 degrees C/150rpm for 48h or 7 days in YM medium containing 0.1% limonene. Great part of the 112 strains recovered after 48h and the 126 strains recovered after 7 days were identified as Gram positive bacilli, followed by Gram negative bacilli, yeasts and Gram positive cocci, besides five fungi. About half of the Gram positive and Gram negative bacilli and yeasts and some Gram positive Cocci were resistant to limonene concentrations up to 2% in the medium broth. Amongst them seventy were able to grow in mineral medium containing limonene as sole carbon source. The research described in this paper is the initial step for the exploration of flavor compounds production via biotransformation of limonene, a nonexpensive by-product of citrus industry.