Implementation of the microbiome of a microalgae cultivation system for the evaluation of a novel decontamination method

Large-scale microalgae cultivations are increasingly used for the production of various high-value bioproducts. Due to the process size and economic limitations, contaminations with other microorganism are inevitable in the employed bioreactors. In the present study, we explored the potential of 5-isobutyl-2,3-dimethylpyrazine for the decontamination of such systems. Contaminating microalgae species were identified in an industrial, multistage cultivation process by amplicon sequencing of the 18S rRNA gene fragment. Haematococcus, Chlorella, and Scenedesmus were found to be the three most frequently occurring microalgae genera in the probed reactors. Following their isolation, representatives of each lineage were tested for their susceptibility towards the antimicrobial compound. It was demonstrated that all isolated contaminants are highly susceptible to the employed alkylpyrazine. The highest tolerance towards the bioactive compound was observed with Scenedesmus vacuolatus. Nevertheless, the isolate was entirely deactivated in liquid 1% pyrazine solutions. Additional experiments with the vaporized alkylpyrazine showed unaltered reductions in the viability of treated microalgae. This indicates the suitability of the novel decontamination method for conventional application forms.