Microbially derived off-flavor from geosmin and 2-methylisoborneol: sources and remediation

Microbially derived off-flavors can adversely affect the beverage, food, water, and aquaculture industries. Off-flavor can temporarily be controlled by adopting best management practices such as proper aeration, liming, and dredging, and, more importantly, by avoidance of excessive nutrient use. Research studies focus on the effective means of control with the major emphasis on controlling the odor-causing algae populations and developing effective and selective algicides, which are not always available for use at the right time and can also have adverse impacts on the environment. Furthermore, selective application of synthetic algicides is not always recommended for reasons of inconsistency in the results and concerns regarding the frequent use of these chemicals, such as toxicity, accumulation of free copper, dissolved oxygen voids, increase in toxic ammonia and hydrogen sulfide, pH fluctuation, reduced photosynthetic activity, and reestablishment of algae in nutrient-rich water, thus requiring multiple treatments. Conversely, the plant-derived products appear to be environmentally safe and economical in view of their abundant availability and easy operational process. However, there needs to be more extensive work in this field. Precursors of sesquiterpene synthesis may selectively help to suppress off-flavor-producing species. Bioremedial measures by means of microbial degradation and gene bioaugmentation may be promising and are the subjects of much future research for effective controls.