Microalgal biofilm for post-treatment of wastewater and bioresource recovery

Microalgae, especially with biofilm-forming abilities, are known to be an efficient alternative to treat wastewater. On the other hand, their biomass is reported to contain valuable bioactive compounds making them useful in industries such as food, pharmaceuticals, and cosmetics. However, there is lack of study on the potential of locally isolated microalgae in wastewater treatment or their role in biotechnological applications. This study was aimed to investigate the potential of local biofilm-forming microalgae and their consortia in pollutant removal performance and bioresource recovery. Local microalgae were isolated and grown in synthetic wastewater to determine their ability in reducing nitrogen and phosphorus pollutants while their biomass and lipid production were also determined. Following that, microalgae with promising abilities were selected to form consortia and their potentials were re-evaluated. The biofilm morphology, Total Nitrogen (TN) and Total Phosphorus (TP) removal, biomass production, and lipid profiles were assessed using FESEM, standard colorimetric analyses, gravimetric measurements, and GC–MS, respectively. A total of 24 microalgae were successfully isolated and demonstrated biofilm formation, which was then confirmed by FESEM analysis for selected isolates. After cultivation in synthetic wastewater for seven days, MA18 identified as Nodosilinea nodulosa, and MA7 identified as Leptolyngbya sp., were found to be the highest pollutant remover with 43.5% and 95.0% for TN and TP, respectively, while the highest biomass production was observed in MA23, which is molecularly identified as Leptolyngbya sp., at 90.0% as compared to the initial growth. GC–MS analysis of lipid extraction revealed that C16-C18 were the predominant fatty acids produced by the isolates, indicating their potential for biofuel production, with MA23 producing the broadest fatty acids profile. A total of ten consortia from the combination of microalgae displaying potential abilities was then constructed. Consortium 7 (MA18–MA5–MA22) displayed the highest TN removal rate at 75.2%, while Consortium 1 (MA18–MA7–MA23) demonstrated exceptional TP removal at 99.4%. The highest biomass yield was recorded for Consortium 10 (MA18–MA4–MA22), representing a 50.0% increase from the initial culture. For lipid analysis Consortium 1 (MA18–MA7–MA23) displayed the most diverse fatty acid profile, dominated by saturated fatty acids of C14-C24, with monounsaturated fatty acids. The consortia outperformed individual isolates in TN and TP removal, whereas higher biomass production was observed in individual isolates. These findings demonstrate the potential of locally isolated microalgae in pollutant removal, biomass productivity and biofuel-relevant lipid profiles, indicating promising candidates for biotechnological applications.