Abstract
Microalgae are considered a potential source of valuable compounds for multiple purposes and are potential agents for bioremediation of aquatic environments contaminated with different pollutants. This work evaluates the use of agricultural waste, unsterilized and anaerobically digested, to produce biomass from a strain of Chlorella sorokiniana. Furthermore, the presence of bacteria in these wastes was investigated based on the bacterial 16S rRNA gene sequencing. The results showed a specific growth rate ranging between 0.82 and 1.45 day−1, while the final biomass yield in different digestate-containing treatments (bacterial-contaminated cultures) ranged between 0.33 and 0.50 g L−1 day−1. Besides, substantial amounts of ammonium, phosphate, and sulfate were consumed by C. sorokiniana during the experimental period. The predominant bacteria that grew in the presence of C. sorokiniana in the effluent-containing treatments belonged to the genera Chryseobacterium, Flavobacterium, Sphingomonas, Brevundimonas, Hydrogenophaga, Sphingobacterium, and Pseudomonas. Therefore, this microalga can tolerate and grow in the presence of other microorganisms. Finally, these results show that anaerobically digested agricultural waste materials are a good substitute for growth media for green microalgae; however, phosphate and sulfate levels must also be controlled in the media to maintain adequate growth of microalgae.
Highlights
Microalgae are deservedly considered promising renewable sources of various valuable compounds—proteins, lipids, pigments, antioxidants, as well as valuable food and feed additives
The growth of microalgae and biomass productivity when grown in wastewater or anaerobic digester effluent depend on different factors [28]
The microalgal strain Chlorella sorokiniana AM-02 was tested in our previous study [27], in which we identified the optimal growth conditions in a standard Bold’s Basal Medium (BBM)
Summary
Microalgae are deservedly considered promising renewable sources of various valuable compounds—proteins, lipids, pigments, antioxidants, as well as valuable food and feed additives. Bohutskyi with colleagues [12,13] proved that only a few algae of the genera Chlorella and Scenedesmus could grow efficiently in the bacterial-contaminated wastewater media Chlorella species, such as Chlorella vulgaris and Chlorella sorokiniana, are admirable for autotrophic, heterotrophic, and mixotrophic growth. Extracts of microalgae of the genera Chlorella and Scenedesmus positively affect the germination of root crops [22] Researchers in this area pay great attention to optimizing the nutritional conditions in order to increase the biomass yield of these photosynthetic microorganisms and the productivity of individual products of their metabolism. The gaseous product of the anaerobic process, effluents (digestates) are generated, which are rich in nitrogen and phosphorus compounds They can be considered as inexpensive and suitable media for growing microalgae [16,23]. Bacterial 16S rRNA gene fragments were examined to analyze the level of bacterial contamination in the media
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