Co-Cultivation of Fungal and Microalgal Cells as an Efficient System for Harvesting Microalgal Cells, Lipid Production and Wastewater Treatment

Abstract

The challenges which the large scale microalgal industry is facing are associated with the high cost of key operations such as harvesting, nutrient supply and oil extraction. The high-energy input for harvesting makes current commercial microalgal biodiesel production economically unfeasible and can account for up to 50% of the total cost of biofuel production. Co-cultivation of fungal and microalgal cells is getting increasing attention because of high efficiency of bio-flocculation of microalgal cells with no requirement for added chemicals and low energy inputs. Moreover, some fungal and microalgal strains are well known for their exceptional ability to purify wastewater, generating biomass that represents a renewable and sustainable feedstock for biofuel production. We have screened the flocculation efficiency of the filamentous fungus A. fumigatus against 11 microalgae representing freshwater, marine, small (5 µm), large (over 300 µm), heterotrophic, photoautotrophic, motile and non-motile strains. Some of the strains are commercially used for biofuel production. Lipid production and composition were analysed in fungal-algal pellets grown on media containing alternative carbon, nitrogen and phosphorus sources contained in wheat straw and swine wastewater, respectively. Co-cultivation of algae and A. fumigatus cells showed additive and synergistic effects on biomass production, lipid yield and wastewater bioremediation efficiency. Analysis of fungal-algal pellet's fatty acids composition suggested that it can be tailored and optimised through co-cultivating different algae and fungi without the need for genetic modification.

Solar-to-fuel conversion in algae and cyanobacteria

“…Microbial fl occulants have been isolated from auto-fl occulating microalgal cultures grown on wastewater (Manheim and Nelson 2013 ;Guo et al 2013 ). Cocultivation of microalgae with a fi lamentous fungus has been reported to induce fl occulation with an effi ciency of 90 % after the fi rst 24 h, with additional synergistic effects on total biomass yield, on the level and composition of lipids, and on the effi ciency of wastewater treatment (Wrede et al 2014 ). Both cocultivating partners contribute to the total biomass, that was found to be higher than the additive biomass.…”

“…Both cocultivating partners contribute to the total biomass, that was found to be higher than the additive biomass. Moreover, cocultivation has the capacity to tailor the composition of fatty acids without the need for genetic engineering, suggesting benefi ts of this approach on both biomass harvesting and lipid biosynthesis for biodiesel production (Wrede et al 2014 ).…”

Enhancing Algal Biomass and Lipid Production through Bacterial and Fungal Co-Culture

“…Although positive growth is demonstrated, there is a disproportionate focus concerned over using filamentous fungi to facilitate the harvesting of algae cells and disregard the lipid content of algae (Zhang and Hu 2012;Gultom and Hu 2013;Wrede et al 2014). And when lipid content is considered in a co-cultivation scheme of algae and fungi, the only explanations for the stimulation in biomass and lipid increase is an improved uptake of glucose from the medium and an induced fungal cellulase activity for the consumption of algal cell debris (Xie et al 2013).…”

Estudo químico de cianobactérias marinhas e do cultivo misto entre a linhagem Geitlerinema sp CENA556 e o fungo Trichoderma atroviride, endófito da alga marinha Bostrychia tenella

“…Neste contexto, o cultivo misto entre diferentes microrganismos, ao invés de culturas independentes, é uma abordagem usualmente praticada em microbiologia para promover interações diretas que podem estimular o acúmulo de produtos naturais presentes constitutivamente ou induzir à expressão de vias biossintéticas silenciadas levando à produção de novos compostos (ANGELIS et al, 2012;BRAKHAGE, 2013;OLA et al, 2013;SANTOS & REIS, 2014;WREDE et al, 2014). Estudo com fungos associados da água viva Nemopilema nomurai, envolvendo cultivo independente e cultivo misto entre eles, mostraram que houve diferenças nos níveis da produção de metabólitos antibacterianos e antifúngicos produzidos (YUE et al, 2015).…”

“…Assim, até o momento, nenhuma pesquisa visando à produção de fármacos foi descrita. A associação (fungo e cianobactéria), no entanto, não é uma novidade, ela existe naturalmente a mais de 400 milhões de anos, na forma de líquens (WREDE et al, 2014). Estes que, por sua vez, podem ser formados pela associação entre fungos e algas ou fungos e cianobactérias, apresentam características interessantes como a produção de metabólitos secundários com aplicação na indústria farmacêutica, alimentícia, cosmética e etc (SUZUKI et al, 2016;SANTOS & REIS, 2014).…”