Microbial Degradation of 2‐Methylisoborneol in Forest Soil**

Abstract

Microorganisms use a complex array of chemical compounds to interact with their surroundings. They produce and process different molecules in response to changes in the environment or in their metabolism. One of the most well‐known volatile organic compounds produced by microorganisms is the C11‐terpenoid 2‐methylisoborneol (2‐MIB), which has received attention because of the off‐flavor it confers to fresh and reservoir water as well as to cultured fish. Cleaning water supplies of the off‐flavor 2‐MIB has been of interest for the scientific community for years, with the use of techniques that are either expensive, e. g., activated carbon, or create toxic byproducts, e. g., ozonation. In the present study, soil samples from nature were collected from a forest and the volatile organic compounds produced by microbes were extracted and analyzed with focus on non‐canonical terpenoid structures. HS‐SPME‐GC/MS analysis of soil samples revealed 1‐methylcamphene (1‐MC), 2‐methylenebornane (2‐MB) and 2‐MIB as C11‐terpenoids. Due to the high 1‐MC/2‐MIB ratio compared to previous reports, it was hypothesized that microbial degradation of 2‐MIB was in place. Addition of synthetic 2‐MIB to biologically active soil revealed complete degradation of the pollutant to 2‐MB, 1‐MC and 2‐methyl‐2‐bornene (2‐M2B). The results suggest the potential of using respective natural microorganisms for biodegradation of 2‐MIB, with applications in water treatment, fishery and soil ecology.

Biodegradation of 2-Methylisoborneol (2-MIB) by Single-Bacterium Isolations from Biological Filters in Drinking Water Treatment Plants

“…16 Drummond et al reported the in-place biodegradation of both naturally generated and spiked synthetic 2-MIB in soil samples. 17 Shao and Du reported that not only the bacteria themselves but also the enzymes separated from 2-MIB degraders also reduced the 2-MIB concentration and linked the mechanism with NADdependent dehydratase. 18 Other strains of bacteria were also demonstrated to degrade 2-MIB efficiently, including Micrococcus sp., Pseudomonas sp., Flavobacterium sp., Acidobacteriacea, Brevibacterium, and Bacillus fusiformis.…”

“…2-MIB degraders were also successfully isolated from the sludge of a fish culture system and demonstrated to effectively reduce 2-MIB from ∼500 to <100 ng/L over 3 days . Drummond et al reported the in-place biodegradation of both naturally generated and spiked synthetic 2-MIB in soil samples . Shao and Du reported that not only the bacteria themselves but also the enzymes separated from 2-MIB degraders also reduced the 2-MIB concentration and linked the mechanism with NAD-dependent dehydratase .…”

Odor Characteristics of Novel Non-Canonical Terpenes

“…The methylated monoterpene 2-methylisoborneol 1 has been described, for example, in Streptomyces and Actinomyces species with an unpleasant muddy flavor and an extremely low odor threshold of 0.042 µg L −1 in water [4]. Furthermore, 2-methyl-2-bornene 2, 1-methylcamphene 3, and 2-methylenebornane 4 have been described in forest soil [5], and the methylated monoterpenes and monoterpenoids 2-methylgeraniol 5, 2-methyllinalool 6, 2-methyllimonene 7, and 2-methyl-α-terpineol 8, have been identified as products of Nannocystis exedens [6] (Figure 1). Harms et al investigated methylated sesquiterpenes such as iso-β-elemene and isogermacrene, which were synthesized with a sesquiterpene synthase and showed potential as flavor compounds.…”