Effects of relevant ammonium chloride concentrations on biomass and off-flavor compound production by Streptomyces luridiscabiei originating from a recirculating aquaculture system

ABSTRACT

The preharvest off-flavors “earthy” and “musty” can occur in fish raised in recirculating aquaculture systems (RAS) rendering them unpalatable and unmarketable. These off-flavors are due to the accumulation of geosmin and 2-methyisoborneol (MIB) in the fish flesh. Previously, Streptomyces luridiscabiei was isolated from a RAS and determined to produce both off-flavor compounds. Because nutritional factors can impact production of these off-flavor compounds by actinomycetes, cultures of S. luridiscabiei were incubated under different ammonium chloride concentrations for 28 days and evaluated for biomass, geosmin, and MIB production. Similar biomass production by S. luridiscabiei occurred at the different ammonium chloride concentrations throughout most of the study period. Conversely, significantly higher (P < .05) concentrations of geosmin and MIB were produced by S. lurisdiscabiei at the highest ammonium chloride concentration (7.5 mg/L) at 28 days. These preliminary results indicate that maintenance of total ammonia nitrogen concentrations below 1 mg/L may reduce concentrations of geosmin and MIB in the RAS water.

KEYWORDS:

• Geosmin
• 2-methylisoborneol
• off-flavor
• rainbow trout
• streptomyces

Acknowledgments

The technical assistance of Dewayne Harries and Phaedra Page is greatly appreciated.

Disclosure statement

No potential conflict of interest was reported by the author.