Abstract
Microalgae exhibit extensive potential for counteracting imminent challenges in the nutraceutical, pharmaceutical, and biomaterial sectors, but lack economic viability. Biotechnological systems for contamination control could advance the economic viability of microalgal feedstock, but the selection of suitable strains that sustainably promote microalgal productivity remains challenging. In this study, total diversity in phototrophic Chlorella vulgaris cultures was assessed by amplicon sequencing comparing cultures subjected to five different cultivation conditions. Overall, 12 eukaryotic and 53 prokaryotic taxa were identified; Alphaproteobacteria (36.7%) dominated the prokaryotic and C. vulgaris (97.2%) the eukaryotic community. Despite altering cultivation conditions, 2 eukaryotic and 40 prokaryotic taxa remained stably associated with C. vulgaris; diversity between systems did not significantly differ (P > 0.05). Among those, 20 cultivable taxa were isolated and identified by 16S rDNA sequencing. Subsequently, controlled co‐cultures were investigated showing stable associations of C. vulgaris with Sphingopyxis sp. and Pseudomonas sp.. Out‐competition of C. vulgaris due to ammonium or phosphate limitation was not observed, despite significantly elevated growth of Sphingopyxis sp. and Tistrella sp.. (P < 0.05). Nevertheless, C. vulgaris growth was impaired by Tistrella sp.. Hence, the study provides a selection of stable indigenous prokaryotes and eukaryotes for artificially tailoring microbial biocenoses. Following a bottom‐up approach, it provides a base for controlled co‐cultures and thus the establishment of even more complex biocenoses using interkingdom assemblages. Such assemblages can benefit from functional richness for improved nutrient utilization, as well as bacterial load control, which can enhance microalgal feedstock production through improved culture stability and productivity.
Highlights
Laboratory of Sustainable Food Processing, Institute of Food, Nutrition and Health, Swiss Federal Institute of Technology (ETH), Schmelzbergstrasse 9, 8092 Zu€rich, Switzerland
The pre-culture was maintained for 1 year by serial sub-culture, where at the end of the exponential growth phase cultures were inoculated to a dry weight (DW) of 0.2–0.3 g Á LÀ1 using fresh diluted seawater nitrogen (DSN) medium, which was inferred from a linear fit for optical density (OD) at 750 nm and C. vulgaris DW, as described elsewhere (Helisch et al 2016)
C. vulgaris dominated the eukaryotic community of each cultivation condition investigated, accounting for 99.9% of total sequence reads in the pre-culture, 99.5% in shaking incubator (SI), 95.9% in biobench flat plate airlift photobioreactor (BB), and 94.3% in flat panel airlift PBR (FPA) samples
Summary
Laboratory of Sustainable Food Processing, Institute of Food, Nutrition and Health, Swiss Federal Institute of Technology (ETH), Schmelzbergstrasse 9, 8092 Zu€rich, Switzerland. Total diversity in phototrophic Chlorella vulgaris cultures was assessed by amplicon sequencing comparing cultures subjected to five different cultivation conditions. Eukaryotic and 40 prokaryotic taxa remained stably associated with C. vulgaris; diversity between systems did not significantly differ (P > 0.05). Following a bottom-up approach, it provides a base for controlled co-cultures and the establishment of even more complex biocenoses using interkingdom assemblages. Such assemblages can benefit from functional richness for improved nutrient utilization, as well as bacterial load control, which can enhance microalgal feedstock production through improved culture stability and productivity
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