Growth promotion of three microalgae, Chlamydomonas reinhardtii, Chlorella vulgaris and Euglena gracilis, by in situ indigenous bacteria in wastewater effluent

Abstract

BackgroundMicroalgae are a promising biomass feedstock for biofuels production. The use of wastewater effluent as a nutrient medium would improve the economics of microalgal biofuels production. Bacterial communities in aquatic environments may either stimulate or inhibit microalgal growth. Microalgal productivity could be enhanced if the positive effects of indigenous bacteria could be exploited. However, much is unknown about the effects of indigenous bacteria on microalgal growth and the characteristics of bacterial communities associated with microalgae in microalgae–effluent culture. To assess the effects of the indigenous bacteria in wastewater effluent on microalgal growth, three microalgae, Chlamydomonas reinhardtii, Chlorella vulgaris, and Euglena gracilis, were cultured in two municipal wastewater effluents and one swine wastewater effluent with and without indigenous bacteria for 7 days.ResultsAll microalgae grew better in all effluents with indigenous bacteria than without bacteria. Biomass production of C. reinhardtii, C. vulgaris, and E. gracilis increased > 1.5, 1.8–2.8, and > 2.1-fold, respectively, compared to the axenic cultures of each microalga. The in situ indigenous bacterial communities in the effluents therefore promoted the growth of the three microalgae during 7-day cultures. Furthermore, the total numbers of bacterial 16S rRNA genes in the 7-day microalgae–effluent cultures were 109‒793 times the initial numbers. These results suggest that the three microalgae produced and supplied organic carbon that supported bacterial growth in the effluent. At the phylum and class levels, Proteobacteria (Alphaproteobacteria and Betaproteobacteria) and Bacteroidetes (Sphingobacteriia and Saprospirae) were selectively enriched in all microalgae–effluent cultures. The enriched core bacterial families and genera were functions of the microalgal species and effluents. These results suggest that certain members of the bacterial community promote the growth of their “host” microalgal species.ConclusionTo enhance their own growth, microalgae may be able to selectively stimulate specific bacterial groups from among the in situ indigenous bacterial community found in wastewater effluent (i.e., microalgae growth-promoting bacteria: MGPB). The MGPB from effluent cultures could be used as “probiotics” to enhance microalgal growth in effluent culture. Wastewater effluent may therefore be a valuable resource, not only of nutrients, but also of MGPB to enable more efficient microalgal biomass production.Electronic supplementary materialThe online version of this article (10.1186/s13068-018-1174-0) contains supplementary material, which is available to authorized users.

Chlorella vulgaris and Its Phycosphere in Wastewater: Microalgae-Bacteria Interactions During Nutrient Removal

“…A symbiotic relationship between Chlorella and Bacteroidetes species was described recently, the abundance of Bacteroidetes specifically increased during pre-treatment of dairy-derived liquid digestate (Zhu et al, 2019). In another study Proteobacteria and Bacteroidetes induced growth promotion of three microalgae, Chlamydomonas reinhardtii, C. vulgaris and Euglena gracilis in wastewater and swine manure effluent (Toyama et al, 2018). The genus Exiguobacterium was previously described among the dominant bacteria during domestic wastewater treatment, this specific bacterium was shown to promote Chlorella biomass accumulation and chlorophyll synthesis (Qi et al, 2018;Ren et al, 2019).…”

“…The unknown Pseudomonas (Bin 2) and the unknown Acinetobacter (Bin 3) seem to belong this category, they had a strong interaction with Chlorella and might have been inoculated together into the examined waste liquids. The unknown Enterobacteriaceae and Exiguobacterium, furthermore the representatives of Bacteroidetes are likely to be wastewater-specific bacterial strains (Toyama et al, 2018).…”

Improvement of Euglena gracilis Paramylon Production through a Cocultivation Strategy with the Indole-3-Acetic Acid-Producing Bacterium Vibrio natriegens

“…Interactions between microalgae and bacteria play crucial roles in the growth of microalgae (16,17). Studies have explored the cocultivation of different microorganisms possibly linked with microalgae (18,19). However, microbial interactions between associated bacteria and microalgae are unclear, and few studies have attempted to deploy microbial interactions to microalgal biotechnology.…”

Growth of Chlorella vulgaris using wastewater from Nile tilapia (Oreochromis niloticus) farming in a low-salinity biofloc system

“…Chlorella vulgaris is a Chlorophyceae with diameter of 2-10μm (Kulkarni & Nikolov, 2018), and it is a very well-known species of algae used as human food supplement (Oliveira, Almeida, Viveiros, Santos, & Dantas, 2018;Dantas et al, 2019). The C. vulgaris capacity in bioremediation of wastewater is already proven in the literature (Brennan & Owende, 2010;Toyama et al, 2018;Gao et al, 2019), since this species has high potential to reduce the P and N of effluents (Ruiz et al, 2011). However, there is no record of the grow capacity of this microalga in BFT effluents.…”