The structure and diversity of microalgae-microbial consortia isolated from various local organic wastes

Abstract

Pure microalgae cultivation in organic wastes may be hampered by their low adaptation to extreme growth conditions and by the risk of microbial contamination. This work aimed to isolate self-adapted microalgae-microbial consortia able to survive in organic wastes characterized by extreme conditions, to be then proposed for technological application in removing carbon and nutrients from wastes' streams. To do so, sixteen organic wastes with different origins and consistency were sampled.Twelve microbial consortia were isolated from wastes and their eukaryotic and prokaryotic compositions were analyzed by next generation sequencing. Eight eukaryotic communities were dominated by Chlorophyta, led by Chlorella, able to survive in different wastes regardless of chemical-biological properties. Tetradesmus, the second most represented genus, grew preferentially in substrates with less stressing chemical-physical parameters. Chlorella and Tetradesmus were mostly isolated from cow slurry and derived wastes which proved to be the best local residual organic source.

Growth Performance, Biochemical Composition and Nutrient Recovery Ability of Twelve Microalgae Consortia Isolated from Various Local Organic Wastes Grown on Nano-Filtered Pig Slurry

“…pH ranged between 6.4 ± 0.3 and 9.1 ± 0.2, TA varied widely between 2.1 ± 0.1 g and 18.7 ± 0.5 CaCO 3 kg −1 and ammonium content ranged from 0.3 ± 0 up to 3.5 ± 0.4 g kg −1 . The broad variety was also found in the macro and microelement compositions [8].…”

“…The percentage of compositions was referred to the relative abundances of the operational taxonomic units (OTUs) assigned to each genus with respect to the total OTUs assigned to Eukaryotes or Prokaryotes, respectively. Previous findings [8] indicated that the metagenomics compositions of the algae consortia directly isolated from organic wastes (OBs) and then cultivated (CBs) under batch conditions were not significantly different from each other.…”

“…The chemical characterization of the sixteen wastes differed greatly in terms of total solids (TS), volatile solids (VS), pH, ammonium, total alkalinity (TA), total volatile fatty acids and macro and microelement compositions [8]. For instance, TS varied from 15 ± 1 g kg −1 to 257 ± 10 g kg −1 while VS was from 8 ± 0.2 g kg −1 to 221 ± 0.6 g kg −1 .…”

“…All collected samples were immediately brought to the laboratory and stored at 4 • C before further analyses. Preliminary experiments were performed in order to assess the best conditions able to isolate the greatest number of algae [8]. In brief, the sixteen organic waste samples were used as the sources for isolating native microalgae-microbial consortia.…”

“…This work falls within a broad project funded by the Lombardy Region (North Italy), aimed at both studying and isolating indigenous, autochthonous algae-microbial consortia (ACs) from various organic wastes with different origins, forms and consistencies [8], to be used for technological applications to treat organic wastes, removing nutrients and producing useful biomass both in the lab (this paper) and at pilot scale. Thus, the main objective of this study was to examine and compare the potential of twelve microalgae consortia, originally selected from different waste streams rich in diverse N forms, to be cultivated using a nano-filtered permeate from pig slurry as the growth medium, rich in NH 4 -N. We evaluated the growth performance, nutrient removal efficiency and biomass quality in terms of biochemical composition, along with fatty acid and amino acid profiles, to give insight into the most robust algae consortia, especially in regards to their adaptability to NH 4 -N sources.…”