Biofuels produced from photosynthetic microorganisms such as microalgae and cyanobacteria could potentially replace fossil fuels as they offer several advantages over fuels produced from lignocellulosic biomass. In this study, energy production potential in the form of bioethanol was examined using different biomasses derived from the growth of a cyanobacteria-based microbial consortium on a chemical medium and on agro-industrial wastewaters (i.e., dairy wastewater, winery wastewater and mixed winery–raisin effluent) supplemented with a raisin residue extract. The possibility of recovering fermentable sugars from a microbial biomass dominated by the filamentous cyanobacterium Leptolynbgya sp. was demonstrated. Of the different acid hydrolysis conditions tested, the best results were obtained with sulfuric acid 2.5 N for 120 min using dried biomass from dairy wastewater and mixed winery–raisin wastewaters. After optimizing sugar release from the microbial biomass by applying acid hydrolysis, alcoholic fermentation was performed using the yeast Saccharomyces cerevisiae. Raisin residue extract was added to the treated biomass broth in all experiments to enhance ethanol production. Results showed that up to 85.9% of the theoretical ethanol yield was achieved, indicating the potential use of cyanobacteria-based biomass in combination with a raisin residue extract as feedstock for bioethanol production.

The marine microalgae Tetraselmis striata was cultivated in drilling waters with different salinities. Growth substrate optimization was performed while the effects of different pH, temperature, photoperiod and CO₂ flow rate on biomass productivity and its composition were studied. Results showed that the strain grew better in 2.8% drilling waters employing the fertilizer Nutri-Leaf together with ΝaHCO₃. A pH value of 8 resulted in high biomass productivity (79.8 mg L⁻¹ d⁻¹) and biomass composition (proteins 51.2% d.w., carbohydrates 14.6% d.w., lipids 27.8% d.w. and total chlorophylls 5.1% d.w.). The optimum cultivation temperature was found to be 25 ± 1 °C which further enhanced biomass productivity (93.7 mg L⁻¹ d⁻¹) and composition (proteins 38.7% d.w., carbohydrates 20.4% d.w., lipids 30.2% d.w., total chlorophylls 5.1% d.w.). Photoperiod experiments showed that continuous illumination was essential for biomass production. A 10 mL min⁻¹ flow rate of CO₂ lead to biomass productivity of 87.5 mg L⁻¹ d⁻¹ and high intracellular content (proteins 44.6% d.w., carbohydrates 10.3% d.w., lipids 27.3% d.w., total chlorophylls 5.2% d.w.). Applying the optimum growth conditions, the produced biomass presented high protein content with adequate amino acids and high percentages of eicosapentaenoic acid (EPA), indicating its suitability for incorporation into conventional fish feeds. In addition, this study analyzed how functional parameters may influence the uptake of nutrients by Tetraselmis.

Poultry litter extract (PLE) was treated using a microbial consortium dominated by the filamentous cyanobacterium Leptolyngbya sp. in synergy with heterotrophic microorganisms of the poultry waste. Laboratory- and pilot-scale experiments were conducted under aerobic conditions using suspended and attached growth photobioreactors. Different dilutions of the extract were performed, leading to different initial pollutant (nitrogen, phosphorus, dissolved chemical oxygen demand (d-COD), total sugars) concentrations. Significant nutrient removal rates, biomass productivity, and maximum lipid production were determined for all the systems examined. Higher d-COD, nitrogen, phosphorus, and total sugars removal were recorded in the attached growth reactors in both laboratory- (up to 94.0%, 88.2%, 97.4%, and 79.3%, respectively) and pilot-scale experiments (up to 82.0%, 69.4%, 81.0%, and 83.8%, respectively). High total biomass productivities were also recorded in the pilot-scale attached growth experiments (up to 335.3 mg L⁻¹d⁻¹). The produced biomass contained up to 19.6% lipids (w/w) on a dry weight basis, while the saturated and monounsaturated fatty acids accounted for more than 70% of the total fatty acids, indicating a potential biodiesel production system. We conclude that the processing systems developed in this work can efficiently treat PLE and simultaneously produce lipids suitable as feedstock in the biodiesel manufacture.

Marine microalgae are considered an important feedstock of multiple valuable metabolic compounds of high biotechnological potential. In this work, the marine microalga Tetraselmis striata was cultivated in different scaled photobioreactors (PBRs). Initially, experiments were performed using two different growth substrates (a modified F/2 and the commercial fertilizer Nutri-Leaf (30% TN—10% P—10% K)) to identify the most efficient and low-cost growth medium. These experiments took place in 4 L glass aquariums at the laboratory scale and in a 9 L vertical tubular pilot column. Enhanced biomass productivities (up to 83.2 mg L⁻¹ d⁻¹) and improved biomass composition (up to 41.8% d.w. proteins, 18.7% d.w. carbohydrates, 25.7% d.w. lipids and 4.2% d.w. total chlorophylls) were found when the fertilizer was used. Pilot-scale experiments were then performed using Nutri-Leaf as a growth medium in different PBRs: (a) a paddle wheel, open, raceway pond of 40 L, and (b) a disposable polyethylene (plastic) bag of 280 L working volume. Biomass growth and composition were also monitored at the pilot scale, showing that high-quality biomass can be produced, with important lipids (up to 27.6% d.w.), protein (up to 45.3% d.w.), carbohydrate (up to 15.5% d.w.) and pigment contents (up to 4.2% d.w. total chlorophylls), and high percentages of eicosapentaenoic acid (EPA). The research revealed that the strain successfully escalated in larger volumes and the biochemical composition of its biomass presents high commercial interest and could potentially be used as a feed ingredient.

BACKGROUND: Fruit juices are an exceptional source of nutrients; however, due to their short shelf‐life and vulnerability to microbial degradation, large volumes of juice are regularly discarded worldwide. As a wastewater, discarded fruit juices (DFJ) possess high organic loads with significant amounts of nitrogen and phosphorus, making them a suitable substrate for microbial growth and to produce natural bioactive compounds.RESULTS: Discarded fruit juices (DFJ) were treated and simultaneously valorized (producing microbial lipids) using a microbial consortium dominated by the photosynthetic cyanobacterium Leptolyngbya sp. The effects of N:P and C:N ratios on growth and lipid production were examined, along with the ability of the consortium to biotreat DFJ in laboratory‐scale (LS) reactors. Using the optimum nutrient ratios (N:P 5:1, C:N 50.2:1), scaled‐up reactors (aquariums) were then tested under suspended and attached growth conditions. The biomass produced was further exploited for lipid production and the results revealed that Leptolyngbya sp. was able to produce up to 19% d.w. lipids and simultaneously efficiently treat DFJ. High dissolved‐chemical oxygen demand (d‐COD), total nitrogen, and PO₄³⁻ removal rates (85.0% and 93.9%, 93.4% and 95.2%, 84.6% and 83.9%, respectively) were achieved in both the suspended and attached growth systems, along with high biomass productivities (316.3, 340.0 mg L⁻¹ day⁻¹, respectively).CONCLUSION: The biological approach used in this study demonstrated that is possible to exploit DFJ and achieve satisfactory lipid contents (up to 19% d.w.) using a cyanobacterial‐based consortium. © 2023 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).