Submitted to: Entomologia Experimentalis et Applicata
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/30/2003
Publication Date: 4/15/2003
Citation: Vega, F.E., Dowd, P.F., Blackburn, M.B., Kurtzman, C.P. 2003. Possible degradative roles of a coffee berry borer-associated yeast. Entomologia Experimentalis et Applicata.
Interpretive Summary: The coffee berry borer is the most devastating pest of coffee throughout the world. Eggs are deposited inside coffee berries, and insects feed on the coffee seed, severely reducing yields. Of more than 800 insects reported on coffee, the coffee berry borer is the only one that has developed the ability to exploit the coffee bean as a food source. This is remarkable due to the many reports of caffeine toxicity to insects and the caffeine content in the coffee seed which averages 1.1 - 1.7% in Coffea arabica L. and 2 - 3% in C. canephora (robusta). During routine examinations of coffee berry borers for microbial pathogens, we detected the presence of a yeast within the insect. This was interesting because yeasts in insects are known to detoxify plant toxins or to produce enzymes that help in digestion of food material. Thus, we became interested in determining the possible role of the coffee berry borer yeast. Our results indicate that the yeast does not play a role in caffeine detoxification but is involved in the production of various enzymes that can be used for nutrient utilization. These findings, which add to the knowledge on the basic biology of the insect, indicate that a possible mechanism for reducing the insect's ability to use the coffee seed as a food source might involve interfering with the yeast.
Technical Abstract: Two yeasts isolated from laboratory reared adult coffee berry borers and from insects collected in the field in Colombia were identified as Pichia burtonii Boidin and Pichia guilliermondii based on 26s ribosomal gene sequences. Liquid culture experiments with media containing different caffeine levels indicate that caffeine levels in a range found within coffee seeds can retard yeast growth. HPLC analysis shows that the yeast does not breakdown caffeine. Isozyme tests of yeast grown on different media substrates indicated that the yeast produced several hydrolytic enzymes, including 1-naphtyl acetate esterase, 1-naphthyl phosphatase, and naphthyl glycosidase. It appears the yeast does not detoxify caffeine, but produces enzymes that detoxify esters and help with nutrient utilization.