Molecular identification, biomass, and biochemical composition of the marine chlorophyte Chlorella sp. MF1 isolated from Suez Bay

Distribution, screening and biochemical characterization of indigenous microalgae for bio-mass and bio-energy production potential from three districts of Pakistan

Abstract Trend of biofuel production from microalgal triacylglycerols is enhancing, because this substrate is a good sustainable and advantageous alternative to oil and gas fuel. In the present study, indigenous micro algal isolates were screened from water (n=30) and soil (n=30) samples collected from three districts of Punjab, Pakistan to evaluate their biofuel production potential. The samples were inoculated on BG – 11 agar medium plates by incubating at room temperature of 25°C providing 1000 lux for 16h light cycle followed by 8h of dark cycle for 15 d. Water samples were found to be rich in microalgae and 65.33% microalgae (49 isolates) were isolated from Faisalabad district. On the basis of microscopic morphology microalgal isolates (n=180) were selected and subjected to lipid detection by Nile red staining assay. Nile red positive isolates (n=23) were processed for biochemical (lipid, protein and carbohydrates) characterization. AIN63 isolate showed higher lipids (17.4%) content as detected by micro vanillin assay. Algal isolate AIN128 showed best protein contents (42.91%) detected by Bradford assay and AIN172 isolate showed higher carbohydrate contents (73.83%) as detected by anthrone assay. The selected algal isolates were also analyzed by Fourier transform infrared (FTIR) spectroscopy for confirmation of carbohydrate, protein and lipid analysis. These indigenous algae have the potential for in-vitro biofuel production from agricultural waste.

Innovative strategies in algal biomass pretreatment for biohydrogen production

Biohydrogen is one of the cleanest renewable energies with a high calorific value. Algal biomass can be utilized as a sustainable feedstock for biohydrogen production via dark fermentation. However, the recovery of fermentable sugar from algal biomass is challenging because of the diversity and complex cell wall composition and therefore, requires an additional pretreatment step. However, most of the conventional pretreatment strategies suffer from limited technological feasibility and poor economic viability. In this context, this review aims to present the structural complexities of the cell wall of algae and highlight the innovative approaches such as the use of hybrid technologies, biosurfactants, nanoparticles, and genetic engineering approaches for the hydrolysis of algal biomass and improved biohydrogen production. Additionally, a comprehensive discussion of the comparative evaluation of various pretreatment methods, and the techno-economic and life cycle assessment of algal biohydrogen production is also presented in this review.

Physiological responses of marine Chlorella sp. exposed to environmental levels of triphenyltin

Triphenyltin (TPT) is a herbicide and antifouling agent that has been widely used. After TPT flows into water bodies, it will cause toxic effects on marine life. We evaluated the effect of environmental concentration level (0, 10, 100, and 200 ng/L) on the cell density, antioxidant capability, and photosynthesis-related genes in the marine Chlorella sp. The results showed that 10 and 100 ng/L TPT can promote the growth of marine Chlorella sp., 200 ng/L TPT can inhibit the growth of marine Chlorella sp., and the TPT toxicity was accumulative. The chlorophyll composition changed. The content of chlorophyll a in 100 ng/L and 200 ng/L groups was significantly higher than that in the control group (p < 0.05) in 13 days. The content of chlorophyll b in the 100 ng/L and 200 ng/L groups in 1 day and 13 days was significantly different from that in the control group (p < 0.05). The content of total chlorophyll in the 100 ng/L and 200 ng/L groups in 13 days was higher than that in the control group (p < 0.05). The 200 ng/L group began to suffer oxidative damage on the 12th day, and the pigment protein complex responded to oxidative damage through self-feedback regulation. On the 18th day, chld, cao, psy, rbcS, and rbcL genes were downregulated, and psbA gene was upregulated in the 10 ng/L and 100 ng/L groups, which may be a feedback regulation of self-oxidative damage. This paper analyzed toxicity of environmental levels of TPT to marine Chlorella sp., which provided new data support for the comprehensive evaluation of its marine ecological toxicity.

Tertiary amine as an efficient CO2 switchable solvent for extracting lipids from hypersaline microalgae

Considering the momentous cost drivers in energy efficient algal biorefinery processes, a green alternative in extracting lipid from microalgae is anticipated. Switchable solvent system using tertiary amines namely DMBA (Dimethylbenzylamine), DMCHA (Dimethylcyclohexylamine), and DIPEA (Diisopropylethylamine) for lipid extraction from wet hypersaline microalgae was investigated in this study. Interestingly, present study showed that at 1:1 (v/v of fresh DMBA solvent: microalgal biomass), and for 1 h extraction time, the lipid yield was 41.9, 26.6, and 33.3% for Chlorella sp. NITT 05, Chlorella sp. NITT 02, and Picochlorum sp. NITT 04, respectively and for recovered DMBA solvent, at 1:1 (v/v) and for 1 h extraction time, the lipid yield was 40.8, 25.97, and 32%, respectively. Similarly, lipid extraction using DMCHA solvent for Chlorella sp. NITT 05, Chlorella sp. NITT 02, and Picochlorum sp. NITT 04 at 1:1 (v/v of solvent: microalgal biomass) and 1 h extraction time showed 34.28, 24.24 and 23.33% lipids, respectively for fresh solvent and 34.01, 24.24 and 23.18% for recovered solvent respectively; while DIPEA was not competent in lipid extraction from three tested microalgae. FAME profile revealed the presence of saturated fatty acids as 43.04%, 40.98%, 38.45% and monounsaturated fatty acids as 28.38%, 27.05%, 23.3% for Chlorella sp. NITT05, Picochlorum sp. NITT04, Chlorella sp. NITT02, respectively. This study attributes Chlorella sp. NITT05 and Picochlorum sp. NITT04 to be ideal algal species for biodiesel production.

Effect of different wavelengths of LED light on the growth, chlorophyll, β-carotene content and proximate composition of Chlorella ellipsoidea

Chlorella ellipsoidea is a freshwater green microalga that has great prospect for the sustainable development of aquaculture industry. Microalgae require optimal lighting conditions for efficient photosynthesis. The key to cost-effective algal biomass production is to optimize algae growth conditions. This study aimed to investigate the effects of various wavelengths viz. white (380-750 nm), green (510 nm), blue (475 nm), and red (650 nm) light-emitting diodes (LEDs) on the growth, pigment content (chlorophyll-a, chlorophyll-b, and β-carotene), and proximate composition of C. ellipsoidea with a photoperiod of 12 h:12 h light: dark cycle under indoor environmental conditions. C. ellipsoidea was cultured in Bold's Basal Medium for 18 days. The cell density (125.36×10⁵ cells ml^-1), cell dry weight (58.9 ± 4.57 mg L^-1), optical density (1.66 ± 0.08 g L^-1), chlorophyll-a (7.31 ± 0.04 μg ml^-1), chlorophyll-b (2.73 ± 0.13 μg ml^-1), and β-carotene (0.39 ± 0.04 μg ml^-1) content of C. ellipsoidea were significantly (P < 0.05) higher at 15^th-day when cultured under blue LED light exposure. Significantly lower growth and nutritional values were obtained under red LED light exposure compared to the control and other LEDs spectra. In Pearson correlation analysis, the cell density and cell dry weight values showed a strong positive correlation with the values of pigment contents of C. ellipsoidea in all the treatments. The LEDs light spectra showed significant effects on proximate composition of C. ellipsoidea. Protein and lipid contents of C. ellipsoidea were significantly higher in blue LED growth conditions compared to white, green, and red LEDs. C. ellipsoidea cells were 3-7.04 μm in size and the maximum area of the cell was 38.94 μm² in blue LED treatment. Results of this study demonstrated that blue LED light spectra was the most suitable condition to induce nutritionally rich biomass production of C. ellipsoidea, which can be used as a potential source of fish feed towards sustainable aquaculture.