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United States Department of Agriculture

Agricultural Research Service

Research Project: MITIGATION OF OFF-FLAVORS IN CATFISH AQUACULTURE

Location: Food Processing and Sensory Quality Research

Title: Biotransformations of 2-methylisoborneol by Terpene-Degrading Bacteria

Authors
item Eaton, Richard
item Sandusky, Peter - TULANE UNIVERSITY

Submitted to: American Society for Microbiology
Publication Type: Abstract Only
Publication Acceptance Date: February 17, 2007
Publication Date: May 21, 2007
Citation: Eaton, R.W., Sandusky, P. 2007. Biotransformations of 2-methylisoborneol by Terpene-Degrading Bacteria. American Society for Microbiology. 21-25.

Technical Abstract: 2-Methylisoborneol (MIB) is produced by a variety of bacteria including actinomycetes and cyanobacteria. When it is present, it gives a camphoraceous earthy off-flavor and smell to farm-raised catfish or drinking water. One way to solve the problem of MIB in catfish ponds or reservoirs might be to remove it by treatment with MIB-degrading bacteria. Although it has been difficult to isolate bacteria capable of growing with MIB, several bacterial strains that can transform MIB have been obtained from existing stocks and by new enrichment with other terpenes, including camphor, limonene, and '-pinene. In initial screening experiments, methylene chloride extracts of terpene-grown bacteria incubated with MIB were analyzed by GC-MS. Three patterns of MIB biotransformation were identified: (i) Camphor-degrading Rhodococcus sp. strain NCIMB 9784 converts MIB to a single product, trans-2,3-dihydroxy-2-methylbornane (identified by GC-MS, 13C-NMR, and 1H-NMR). (ii) Camphor-degrading Pseudomonas sp. strain SWS3-camc and others convert MIB to three oxidation products (differentiated by GC-MS). The major product has been identified as 2,6-dihydroxy-2-methylbornane (by GC-MS, 13C-NMR, and 1H-NMR). (iii). R-Limonene-degrading Pseudomonas sp. strain 19-rlim and S-'-pinene-degrading Pseudomonas sp. strain SBR-sapi dehydrate MIB to 2-methylbornene. This is probably the most interesting and useful transformation of the three, as it eliminates the tertiary alcohol (considered to be responsible for the earthy off-flavor). It also provides a chemical intermediate that can be acted on by a new group of bacteria. Thus several bacterial strains have been shown to catalyze the removal of 2-methylbornene with the accumulation of less volatile, but not yet identified metabolites.

Last Modified: 4/23/2014
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