Bioprospecting and selection of tolerant strains and productive analyses of microalgae grown in vinasse

Sustainable treatment of sugarcane vinasse using Chlorella sp. in scalable airlift flat-panel photobioreactors: nutrient removal and biomass valorization

The global production of sugarcane ethanol generates vast amounts of vinasse, a liquid waste by-product requiring treatment to mitigate environmental impacts. Using vinasse as a feedstock for microalgae cultivation offers a sustainable alternative. This study evaluates the performance of the native strain Chlorella sp. MC18 in internal-loop airlift flat-panel photobioreactors (PBR) for treating industrial raw sugarcane vinasse (SCV) while producing biomass. Cultures were grown in diluted, centrifugation-pretreated SCV (5-25% v/v) as the sole nutrient source, with CO2 supplied by aeration. The best results were obtained with 10% SCV. Nutrient removal efficiencies reached up to 99% for nitrates and 90% for phosphates, with reduction in chemical oxygen demand (COD) exceeding 75% at 5-10% SCV. The highest specific growth rate (0.711 day-1) and biomass productivity (116 mg L-1 day-1) occurred at 10% SCV, maintaining stable pH control (8.2-8.5). The PBR design enabled scalable, reproducible growth kinetics while minimising biofouling. Biomass from 10% SCV holds significant potential for energy recovery (20.24 kJ g-1) and production of high-value product pools (lipids, carbohydrates, proteins, and carotenoids). These results demonstrate the feasibility of scaling up the PBR design for integrated vinasse treatment with Chlorella and biomass valorisation, reinforcing the concept of an agro-industrial sector biorefinery.

The need for smart microalgal bioprospecting

Microalgae's adaptability and resilience to Earth's diverse environments have evolved these photosynthetic microorganisms into a biotechnological source of industrially relevant physiological functions and biometabolites. Despite this, microalgae-based industries only exploit a handful of species. This lack of biodiversity hinders the expansion of the microalgal industry. Microalgal bioprospecting, searching for novel biological algal resources with new properties, remains a low throughput and time-consuming endeavour due to inefficient workflows that rely on non-selective sampling, monoalgal culture status and outdated, non-standardized characterization techniques. This review will highlight the importance of microalgal bioprospecting and critically explore commonly employed methodologies. We will also explore current advances driving the next generation of smart algal bioprospecting focusing on novel workflows and transdisciplinary methodologies with the potential to enable high-throughput microalgal biodiscoveries. Images adapted from (Addicted04 in Wikipedia File: Australia on the globe (Australia centered).svg. 2014.; Jin et al. in ACS Appl Bio Mater 4:5080-5089, 2021; Kim et al. in Microchim Acta 189:88, 2022; Tony et al. in Lab on a Chip 15, 19:3810-3810; Thermo Fisher Scientific INC. in CTS Rotea Brochure).

Bioremediation potential of the Chlorella and Scenedesmus microalgae in explosives production effluents

This study explores microalgae-based bioremediation for treating black gunpowder production effluents, an understudied yet environmentally significant stream. Two native microalgae, Chlorella sp. MC18 (CH) and Scenedesmus sp. MJ23-R (SC), were assessed for growth kinetics and nutrient removal capabilities in culture media containing different proportions of untreated raw wastewater. Results show both species thrived in 100 % raw wastewater, displaying robust growth and substantial biomass production in parallelepiped-shaped photobioreactors. SC showed superior performance, with higher maximum specific growth rate (0.549 d-1), biomass yield (454.57 mg L-1) and biomass productivity (64.94 mg L-1 d-1) compared to CH (0.524 d-1, 380.60 mg L-1, 54.37 mg L-1 d-1, respectively). The use of 100 % raw wastewater as a culture medium eliminated the need for additional freshwater input, thus reducing the water footprint. The bioremediation process also resulted in a high removal efficiency in turbidity (>95 % CH, >76 % SC), total suspended solids (>93 % CH, >74 % SC), biochemical oxygen demand (BOD5) (>62 % CH, >93 % SC) and chemical oxygen demand (COD) (>63 % CH, >87 % SC), bringing the effluent into compliance with environmental regulations. Although nitrogen (>45 % CH, >57 % SC) and sulphate (>43 % CH, >35 % SC) removal efficiencies was high, potassium bioremediation was limited (<6 %). The proximate chemical composition of the microalgal biomass revealed different allocations to carbohydrates, lipids and proteins. The results suggest promising applications for biofuel production and aquaculture. This research highlights the potential of microalgae-based bioremediation for sustainable wastewater management in the explosives industry, contributing to the UN Sustainable Development Goals and promoting green industrial practices.