Microalgae on distillery wastewater treatment for improved biodiesel production and cellulose nanofiber synthesis: A sustainable biorefinery approach.

Sugarcane spent wash generates waste at a large scale that impacts the environment, hence the classic waste reuse technology needs to be implemented. An integrated approach of spent wash and microalgae cultivation to produce biodiesel has gained momentum in recent times. However, the microalgae technology lacks the functional utilization of de-oiled microalgae biomass (DOB). This study proposed the development of a microalgae-based advanced process for distillery spent wash treatment, biomass recovery for biodiesel and utilizing algal residue as a step towards waste management. A novel microalga Coelastrella sp KJ-04 grown in distillery spent wash represented with high biomass (4.61g/L) and lipid production (3.6 g/L). The significant reduction in Chemical Oxygen Demand (COD, 49.3%), Total Nitrogen (TN, 49.7%), Total Phosphorous (TP, 21.8%), Total Organic Carbon (TOC, 40.2%), Total Sulphur (S, 37.2%) and Potassium (K, 42.5%) were achieved in spent wash. The extracted lipids of Coelastrella sp KJ-04 were converted to Fatty acid methyl ester (FAME) and examined by Gas chromatography -mass spectrometry (GC-MS) to observe the suitability for biodiesel prospect. The de-oiled biomass (DOB) was utilized for the synthesis of Cellulose nanofibers (CNF), purified and estimated with a diameter ranging between 20 and 27 nm. The crystalline structure and functional group of CNF were analyzed by X-ray diffraction (XRD) and Fourier Transform infrared spectroscopy (FTIR). The unprecedented work demonstrated the microalgae biorefinery approach for spent wash remediation, biodiesel synthesis and simultaneous production of biodegradable CNF from algal residue to support waste-free technology. In future, CNF can be reinforced into material for concrete as it could be the smart alternative to replace synthetic cement plastics.

Synthesis of two different zinc oxide nanoflowers and comparison of antioxidant and photocatalytic activity.

Nanoflowers are a newly developed class of nanoparticles that show flower-like structures and attract much attention due to their simple preparation methods, high stability, and increased efficiency. The aim of the study is to investigate a strong alternative to reduce the severity of infection and increase the treatment of wastewater by exhibiting biofilm inhibition in medical and environmental applications of the ZnO-NFs with two different shapes. ZnO-NFs were synthesized by two different processes hydrothermal method (named ZnO-NF1) and the precipitation method (named ZnO-NF2). ZnO-NFs produced by two different synthesis methods were compared for the photocatalytic and antioxidant efficiency. The effects of Reactive Red 180 (RR180) and Basic Red 18 (BR18) dyes concentration, photocatalyst amount, and reaction time were investigated on dye removal efficiency for photocatalytic experiments. The color was completely removed for 25 mg/L BR18 and RR180 dyes for 75 min and 90 min, respectively, using 1.5 g/L photocatalyst amount using ZnO-NF1. However, 59.18% dye removal efficiency was obtained for 90 min by using a 1.5 g/L ZnO-NF2 photocatalyst for 25 mg/L BR18 dye removal, while a dye removal efficiency of 90.00% was detected for 90 min using 2 g/L ZnO-NF2 for 25 mg/L RR180 dye. Then, comparison of general properties such as antibacterial, antibiofilm, microbial cell viability, DNA fragmentation, antioxidant activities, and antimicrobial photodynamic therapy of ZnO-NFs were investigated. The antioxidant activity of ZnO-NF2 was found to be higher than ZnO-NF1 at each concentration (82.32% and 87.18% for ZnO-NF1 and ZnO-NF2, respectively, at 200 mg/mL).

Characterization of a newly isolated self-flocculating microalga Bracteacoccus pseudominor BERC09 and its evaluation as a candidate for a multiproduct algal biorefinery.

Microalgae have the highest capability to fix the atmospheric carbon and wastewater-derived nutrients to produce high-value bioproducts including lipids and carotenoids. However, their lower titers and single-product-oriented biomass processing have made the overall process expensive. Hence, increased metabolite titer and processing of the biomass for more than one product are required to ensure the commercial robustness of the algal biorefinery. In this study, a newly isolated algal strain was identified as Bracteacoccus pseudominor BERC09 through phylogenetic analysis based on the 18S rRNA gene sequence. Basic characterization of the strain revealed its promising potential to produce carotenoids and lipids. The lipids and carotenoid biosynthesis pathways of BERC09 were further triggered by manipulating the abiotic factors including nitrogen sources (NaNO3, KNO3, NH4Cl, Urea), nitrogen concentrations (0.06-0.36 gL-1), light intensity (150 µmolm-2s-1 to 300 µmolm-2s-1), and light quality (white and blue). Resultantly, 300 µmolm-2s-1 of blue light yielded 0.768 gL-1 of biomass, 8.4 mgg-1 of carotenoids, and 390 mgg-1 of lipids, and supplementation of 0.36 gL-1 of KNO3 further improved metabolism and yielded 0.814 gL-1 of biomass, 11.86 mgg-1 of carotenoids, and 424 mgg-1 of lipids. Overall, the optimal combination of light and nitrogen concurrently improved biomass, carotenoids, and lipids by 3.5-fold, 6-fold, and 4-fold than control, respectively. Besides, the excellent glycoproteins-based self-flocculation ability of the strain rendered an easier harvesting via gravity sedimentation. Hence, this biomass can be processed in a cascading fashion to use this strain as a candidate for a multiproduct biorefinery to achieve commercial robustness and environmental sustainability.