Effect of peracetic acid on levels of geosmin, 2-methylisoborneol, and their potential producers in a recirculating aquaculture system for rearing rainbow trout (Oncorhynchus mykiss)

Abstract

In recirculating aquaculture systems (RAS)s, off-flavors and odors, mainly caused by geosmin (GSM) and 2-methylisoborneol (MIB), can accumulate in the flesh of fish from RAS water, reducing the profitability of production. In this study, peracetic acid (PAA) was applied in three application intervals to pump sumps of rainbow trout (Oncorhynchus mykiss) reared in RAS. Using a real-time polymerase chain reaction (qPCR), the potential off-flavor producers were quantified using geoA and MIB synthase genes. Streptomyces was identified as the major GSM producer, and biofilters showed the highest number of potential off-flavor producers. Concentrations of GSM and MIB were analyzed in the circulating water and in the lateral part of the fish fillet. In water, concentrations up to 51 ng L -1 (GSM) and 60.3 ng L -1 (MIB) were found, while in the fillet, these were up to 9.8 ng g -1 (GSM) and 10.2 ng g -1 (MIB), decreasing with increasing number of PAA applications. PAA applications reduced the levels of off-flavor compounds, although this was insufficient to fully prevent the accumulation of GSM and MIB.

Control of off-flavor compounds in a full-scale recirculating aquaculture system rearing rainbow trout Oncorhynchus mykiss

“…In previous studies, a thick layer of mucus has been observed on fish skin after PAA addition (2.2 mg PAA L −1 1-4 times per week, Lindholm-Lehto et al 2019a). In this study, neither this effect nor any signs of discomfort in fish behavior were observed, which was probably due to the much lower dose of PAA: 15 L PAA d −1 , to inlet water of 32-33 L s −1 (5.2 • 10 −3 -5.4 • 10 −3 L PAA m −3 ), and 4-6 L PAA d −1 to the aeration system of the depuration tanks (1.4 • 10 −3 -2.1 • 10 −3 L PAA m −3 ).…”

“…In particular, Streptomyces, actinomycetes, and myxobacteria are considered to be responsible for GSM and MIB production in RAS (Dickschat et al 2005;Guttman and van Rijn 2008;. In our previous study, Streptomyces was identified as the major GSM producer (Lindholm-Lehto et al 2019a).…”

“…GSM and MIB are produced by terpene synthases as secondary metabolites of a wide variety of microorganisms, such as actinomycetes, cyanobacteria, proteobacteria, and fungi (Dickschat et al 2005;Ludwig et al 2007). In a RAS, a biofilter is often the main reservoir of microbes (Lindholm-Lehto et al 2019a;Rurangwa and Verdegem 2015), but GSM-and MIB-producing bacteria have been found to also colonize other RAS sections (Auffret et al 2013;Guttman and van Rijn 2008;. In particular, Streptomyces, actinomycetes, and myxobacteria are considered to be responsible for GSM and MIB production in RAS (Dickschat et al 2005;Guttman and van Rijn 2008;.…”

“…Most studies of removing or decreasing off-flavor-related issues have been conducted in small-scale or pilot-scale systems (Lindholm-Lehto et al 2019a;. For example, studied the effect of ozonation on off-flavors in water and the flesh of rainbow trout, but the study was performed in a small experimental setup.…”

Phytotherapy in aquaculture: integration of endogenous application with science

“…However, peracetic acid had several limitations and disadvantages. The effectiveness of peracetic acid decreased over time due to peroxide degradation (Lindholm-Lehto et al, 2019;Srivastava et al, 2004). In addition, the by-products of degradation, acetic acid and acetate, encouraged the formation of biofilm which in turn became a protection for opportunistic pathogens (Liu, 2016).…”