Mixotrophic Cultivation of Microalgae in Cassava Processing Wastewater for Simultaneous Treatment and Production of Lipid-Rich Biomass

Abstract

Cassava processing wastewater (CPW) is a highly polluting, liquid residue of cassava processing, usually discarded or treated anaerobically. However, it can serve as a low-cost culture medium for microalgae. After a preliminary evaluation of the growth of 10 microalgal strains in diluted CPW, the microalgae Haematococcus pluvialis SAG 34−1b and Neochloris (Ettlia) oleoabundans UTEX 1185 were selected for cultivation in CPW without a supply of additional nutrients and evaluated for their growth, lipid production, and nutrients removal. Maximal biomass concentrations of 1.79 g·L−1 for H. pluvialis and 3.18 g·L−1 for N. oleoabundans were achieved with 25% CPW medium on the 13th day of growth. The algae H. pluvialis and N. oleoabundans removed 60.80 and 69.16% of the chemical oxygen demand, 51.06 and 58.19% of total nitrate, and 54.68 and 69.84% of phosphate, respectively. On average, lipid productivities reached 0.018 and 0.041 g·L−1 day−1 for H. pluvialis and N. oleoabundans, respectively. Therefore, cultivating these microalgae in diluted CPW is a promising treatment for cassava wastewater with simultaneous valuable biomass production.

Cassava and Microalgae Use in the Food Industry: Challenges and Prospects

“…They rely on organic chemicals found in the media [52]. Sorgatto, Soccol, Molina-Aulestia, de Carvalho, de Melo Pereira, and de Carvalho [53] reported that microalgae grew faster in cassava wastewater and produced lipids similar to synthetic mixotrophic cultures. Another research by Nwanko and Agwa (2021) showed that the optimal ratio of cassava peel water to cassava wastewater (CP:CW) for growth was 160:40.…”

“…Over 99% of ammonia, nitrites, and nitrates, could be reduced. [ microalgae in wastewater [53,61]. Table 3 depicts the cassava wastewater treatment product based on microalgae.…”

Agro-Industrial Wastewaters for Algal Biomass Production, Bio-Based Products, and Biofuels in a Circular Bioeconomy

“…Currently, processes such as filtration, flocculation, and sterilization are also being evaluated as pretreatment for this effluent. However, the most promising current research is using the anaerobic digestion of CPW [17,94]. After pretreatment, the effluent CPW (or its digestate) still contains high amounts of nitrogen, phosphate, and soluble sugars, thus allowing the mixotrophic or heterotrophic microalgae production for bioproducts, such as biomass, biodiesel, or pigments [95].…”

“…By providing nutrients at a meager cost, using residues can reduce expenses in algal production. This is advantageous for already established products, such as PC (phycocyanin, a blue-colored protein from cyanobacteria) and AX (astaxanthin, a carotenoid), and enables the production of new products, such as biofuels and PHAs (polyhydroxyalkanoates, biopolymers produced by some cyanobacteria) [16][17][18]. Some bottlenecks to the massive production of microalgal biomass, such as the low cell concentration in cultures and the consequent need for large cultivation areas and large volumes of culture media and nutrients, can be solved using agro-industry wastewaters.…”

Determination of the efficiency of combination therapies on the bioremediation of petroleum spill aquatic ecosystem

“…It was observed that the remediation setup with cassava starch introduced had the lowest water TPH concentration (223 mg/L) at the end of the experimental period. Sorgatto et al (2021) reported that cassava starch in solution helps in the growth of aquatic microscopic plants. These microscopic plants carry out phytoremediation, which lowers the water's TPH content, and reduces its biological oxygen demand and its chemical oxygen demand.…”