Abstract
BackgroundMicroalgae are coming to the spotlight due to their potential applications in a wide number of fields ranging from the biofuel to the pharmaceutical sector. However, several factors such as low productivity, expensive harvesting procedures and difficult metabolite extractability limit their full utilization at industrial scale. Similarly to the successful employment of enzymatic arsenals from lignocellulolytic fungi to convert lignocellulose into fermentable sugars for bioethanol production, specific algalytic formulations could be used to improve the extractability of lipids from microalgae to produce biodiesel. Currently, the research areas related to algivorous organisms, algal saprophytes and the enzymes responsible for the hydrolysis of algal cell wall are still little explored.ResultsHere, an algal trap method for capturing actively growing microorganisms was successfully used to isolate a filamentous fungus, that was identified by whole-genome sequencing, assembly and annotation as a novel Penicilliumsumatraense isolate. The fungus, classified as P.sumatraense AQ67100, was able to assimilate heat-killed Chlorellavulgaris cells by an enzymatic arsenal composed of proteases such as dipeptidyl- and amino-peptidases, β-1,3-glucanases and glycosidases including α- and β-glucosidases, β-glucuronidase, α-mannosidases and β-galactosidases. The treatment of C.vulgaris with the filtrate from P.sumatraense AQ67100 increased the release of chlorophylls and lipids from the algal cells by 42.6 and 48.9%, respectively.ConclusionsThe improved lipid extractability from C.vulgaris biomass treated with the fungal filtrate highlighted the potential of algal saprophytes in the bioprocessing of microalgae, posing the basis for the sustainable transformation of algal metabolites into biofuel-related compounds.
Highlights
Microalgae are coming to the spotlight due to their potential applications in a wide number of fields ranging from the biofuel to the pharmaceutical sector
It is worth noting that Phi is only metabolizable by few chemolithotrophic bacteria possessing the phosphite dehydrogenase enzyme, such as Pseudomonas stutzeri [20], and an eventual microbial growth in such medium could only be sustained at the expense of C. vulgaris biomass, used here as carbon and phosphate source
The fungus grew in the form of small mycelium balls capable of adsorbing the microalgae that, in turn, conferred to the mycelium a light green colour (Fig. 1b); for its isolation, different mycelium portions were harvested from the algal traps and plated onto solid MEP medium
Summary
Microalgae are coming to the spotlight due to their potential applications in a wide number of fields ranging from the biofuel to the pharmaceutical sector Several factors such as low productivity, expensive harvesting procedures and difficult metabolite extractability limit their full utilization at industrial scale. The enzymatic treatment of algal cell wall exploited CWDE blends from saprophytic fungi obtained by fermentation processes, in which plant materials are used as feed for the microbes [13,14,15]. These enzymatic arsenals were not evolved to hydrolyse the cell walls of microalgae, resulting in lower degradation efficiencies. The enzymatic mixtures consisted of degrading enzymes selected from the most disparate organisms such as chicken, fungi and snails, resulting in highly expensive blends [16, 17] and negatively impacting the production cost of extracted metabolites
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