Effect of selected light spectra on the growth of Chlorella spp. (Chlorophyta)

The possibility for simultaneous production of chemical and electrical energies from a single microalgae cultivation plant is opening a new chapter in the efficient use of resources to maximize biomass productivity. In the current study, the effect of selected monochromatic lights (blue, red and pink) from spectrally selective filters on the biomass productivity of semi-continuously grown Chlorella spp. was investigated under laboratory conditions using light emitting diodes (LEDs). The temperature variations inside of the customized light boxes containing cultures under different light spectra were significantly different (p Pink > Blue > Red. The biomass productivity was highest under the white light (60.07±9.38 mg L-1 d-1 dry weight, DW) and varied significantly (p = 0.004) among the treatments. However, productivities under the white (60.07±9.38 mg L-1 d-1 DW) and pink (56.25±9.85 mg L-1 d-1 DW) lights was statistically insignificant (p = 0.551). The result shows that biomass productivity of the alga, Chlorella spp., can be manipulated through targeted supply of specific spectral bands (e.g. pink light). Therefore, the remaining portions of the spectrum which are not utilized by the alga for growth can potentially be converted to electricity through a robust and highly efficient photovoltaic cell

Proximate and phytochemical composition of the pulp of Tetrapleura tetraptera fruits consumed in Abakaliki, Nigeria

Tetrapleura tetraptera fruits have been used in ethnomedical practice in Nigeria for the treatment of diseases and as spices in food preparation. The proximate and phytochemical composition of the pulp of Tetrapleura tetraptera consumed in Abakaliki is determined. The percentage composition (%) on the basis of dry weight was Carbohydrate (40.12±2.57), Moisture (19.90±1.65), Ash (17.84±1.63), Crude Protein (14.10±1.77), Fats and Oil (8.69±1.82) and Crude Fibre (6.84±0.31). The qualitative phytochemical analysis revealed the presence of saponin, tannin, steroids, terpenoids in very high amount, alkaloids, flavonoid, resin in moderately high concentration while glycosides in trace concentration. The quantitative phytochemical analysis (%) based on dry weight were saponin (5.670±0.294), tannin (3.194±0.323), flavonoid (0.073±0.002), alkaloids (0.633±0.057), phenol (0.373±0.013) and glycosides (0.0072±0.0002). The appreciable abundance of these biologically essential compounds in this plant indicates the potential of the pulp of this fruit as a source of these phytochemicals, justifying the use of the fruit in traditional medicine

Effect of Selected Light Spectra on the Growth of Chlorella spp. (Chlorophyta)

The possibility for simultaneous production of chemical and electrical energies from a single microalgae cultivation plant is opening a new chapter in the efficient use of resources to maximize biomass productivity. In the current study, the effect of  selected monochromatic lights (blue, red and pink) from spectrally selective filters on the biomass productivity of semi-continuously grown Chlorella spp. was  investigated under laboratory conditions using light emitting diodes (LEDs). The temperature variations inside of the customized light boxes containing cultures under different light spectra were significantly different (p < 0.001). Cell density of the alga under the different light treatments was not similar and ranked as White > Pink > Blue > Red. The biomass productivity was highest under the white light  (60.07±9.38 mg L-1 d-1 dry weight, DW) and varied significantly (p = 0.004) among the treatments. However, productivities under the white (60.07±9.38 mg L-1 d-1 DW) and pink (56.25±9.85 mg L-1 d-1 DW) lights was statistically insignificant (p = 0.551). The result shows that biomass productivity of the alga, Chlorella spp., can be manipulated through targeted supply of specific spectral bands (e.g. pink light). Therefore, the remaining portions of the spectrum which are not utilized by the alga for growth can potentially be converted to electricity through a robust and highly efficient photovoltaic cell.Keywords: Biomass productivity, Chlorella spp., Electricity, Light spectra, Photovoltai

Co-cultivation of microalgae and macroalgae for the efficient treatment of anaerobic digestion piggery effluent (ADPE)

Microalgal and macroalgal phytoremediation has been proposed as a practical green solution for the treatment of anaerobically digested piggery effluent (ADPE). This is mainly due to the algae’s inherent ability to strip away and convert inorganic nutrients, especially nitrogen and phosphorous efficiently from various effluents. Our previous Pork-CRC (4A-106 and 4A-108) studies showed the potential of a microalgae consortium that could grow efficiently on undiluted ADPE (up to 1600 mg L-1 of ammonium) and that of a macroalgae consortium (4A-107) which could treat diluted ADPE (below 250 mg L-1 of ammonium). The main advantage of macroalgae over microalgae is their ease of harvest, especially if the aim is to use the generated biomass as a source of animal feed. There is a potential in co-culturing cultures of microalgae and macroalgae to increase the overall efficiency of ADPE treatment and improve the economics related to algal biomass production. In accordance, we evaluated the co-cultivation of both microalgae and macroalgae together in two distinctive studies. For both studies, previously isolated consortium of microalgae consisting of Chlorella and Scendesmus sp. was initially grown on undiluted ADPE until the concentration of ammonium was reduced to desired levels. In order to identify the most suitable and efficient macroalgal species for co-cultivation with microalgae, a preliminary study was conducted to evaluate the growth and nutrient removal of four locally isolated macroalgae on ADPE. In the first co-cultivation study, the ADPE grown microalgae was directly utilized as a cultivation media for the propagation of macroalgae (Cladophora sp.) which was found capable of growing in ADPE up to 150 mg L-1 NH4+. However, despite the different conditions evaluated, the growth and photo-physiology of Cladophora sp. was found to decline and eventually led to its death due to the dominancy of microalgal culture during the co-cultivation period. Subsequently, based on this outcome, an outdoor inclined reactor was customized to evaluate the potential use of attached macroalgal culture as a way of scrubbing available nutrients and microalgae biomass from ADPE post microalgal treatment. Although, the inclined system was very efficient in scrubbing and harvesting microalgae biomass, nevertheless, nutrient removal rates (i.e. ammonium and nitrate) of the co-cultivated system was much lower than the control which was operated using macroalgae only. In this work, despite multiple different approaches and cultivation systems, both algal groups were unable to co-exist for efficient growth in ADPE due to direct competition for available resources and the negative interaction of both algal groups. Nevertheless, through this study, it has been demonstrated that macroalgae could be potentially used for harvesting microalgae grown in ADPE

Bio-based flocculants for sustainable harvesting of microalgae for biofuel production. A review

Energy is indispensable to human existence and sustains economic and individual activities globally. The rising environmental challenges of global warming and other climate changes due to increasing dependence on fossil fuels (coal, petroleum, natural gas) as the primary energy source requires innovation away from carbon-based fossil fuel sources. Hence, the development of renewable and low-emission energy sources becomes imperative to guarantee sustainable economic and human population growth and fuel security. In this context, microalgae biofuels are increasingly appreciated as viable alternative to fossil-based fuels because their biomass can be transformed into various clean fuel commodities such as biodiesel, biogas, and bioethanol in an environmentally-friendly and sustainable manner. However, high energy and financial costs of harvesting microalgal biomass for biofuel production constitute a substantial bottleneck in the industry. Bio-based flocculation methods have recently received increased research attention due to their high efficiency, sustainability, and environmentally-friendly attributes. In this review, the feasibility and performance of bio-based technologies for large-scale, cost-effective and sustainable harvesting of microalgal biomass for biofuel production were evaluated. The review shows that the harvesting efficiencies of bio-based processes are not significantly different from those achieved with energy-intensive traditional biomass separation methods such as centrifugation and membrane filtration. Harvested biomass met the moisture content metrics for biofuel feedstocks. The utilization of natural coagulants in algal biomass recovery is associated with low energy consumption, low environmental impacts and reduced effect on the chemistry of recycled medium. Production of recombinant bioflocculants are emerging but the application in algal biomass harvesting is yet to be reported. Bioflocculation approaches provide opportunities for the integration of photosynthetic biorefineries with bioremediation of wastewaters, and this enhances the potential of microalgae biotechnology for biofuel production

Microalgae-based circular economy approach to upcycle fire extinguisher powder waste

Fire extinguishers are used to contain the imminent risk posed by fire globally. Suitable disposal and utilization of fire extinguisher powder (FEP) waste have developed into a significant challenge due to high nitrogen and phosphorus content. Harnessing the waste as a secondary resource for integrated waste-to-profit enterprises, such as microalgae cultivation for high-value bio-based products, is considered crucial for sustainable production, resource conservation, and mitigating adverse effects on environments. This paper proposes an algae-based circular economy concept to recycle one of the most difficult to treat wastes globally by applying it as a nutrient resource for microalgae biomass production. Hydrophilizing the waste for nutrient release is critical to this valorization pathway due to its hydrophobicity. Ten solvents were tested, of which five, including ethanol/methanol-sodium hydroxide mixtures, acetate, isopropanol, and polysorbate-20, were effective in hydrophilizing the powder waste, without significant differences (p 0.05), except for Chaetoceros muelleri, which had 70% more biomass in control than in the waste medium. The protein and carbohydrate contents of Chlorella biomass cultivated in the waste were not significantly different, though significantly higher than carbohydrate (p < 0.001). FEP waste can act as nitrogen and/or phosphorus fertilizers for algal cultivation without significant growth inhibition. The resulting biomass can be valorized to high-value products such as pigments and animal/aquaculture feed due to more than 50% protein content if it meets permissible regulatory levels of contaminants

Growth comparison of microalgae in tubular photobioreactor and open pond for treating anaerobic digestion piggery effluent

The overwhelming interest in the use of microalgae to handle associated nutrient surge from anaerobic digestion technologies for the treatment of wastewater, is driven by the need for efficient nutrient recovery, greenhouse gas mitigation, wastewater treatment and biomass reuse. Here, the feasibility of growth and ammonium nitrogen removal rate of semi-continuous mixed microalgae culture in paddle wheel-driven raceway pond and helical tubular closed photobioreactor (Biocoil) for treating sand-filtered, undiluted anaerobic digestion piggery effluent (ADPE) was compared under outdoor climatic conditions between June and September 2015 austral winter season. Two Biocoils, (airlift and submersible centrifugal pump driven) were tested. Despite several attempts in using airlift-driven Biocoil (e.g. modification of the sparger design), no net microalgae growth was observed due to intense foaming and loss of culture. Initial ammonium nitrogen concentration in the Biocoil and pond was 893.03 ± 17.0 mg NH4 +-N L-1. Overall, similar average ammonium nitrogen removal rate in Biocoil (24.6 ± 7.18 mg NH4 +-N L-1 day-1) and raceway pond (25.9 ± 8.6 mg NH4 +-N L-1 day-1) was achieved. The average volumetric biomass productivity of microalgae grown in the Biocoil (25.03 ± 0.24 mg AFDW L-1 day-1) was 2.1 times higher than in raceway pond. While no significant differences were detected between the cultivation systems, the overall carbohydrate, lipid and protein contents of the consortium averaged 29.17 ± 3.22, 32.79 ± 3.26 and 23.29 ± 2.15% AFDW respectively, revealing its suitability as animal feed or potential biofuel feedstock. The consortium could be maintained in semi-continuous culture for more than three months without changes in the algal composition. Results indicated that microalgae consortium is suitable for simultaneous nutrient removal and biomass production from piggery effluent

Chlorella sp. growth under batch and fed-batch conditions with effluent recycling when treating the effluent of food waste anaerobic digestate

Anaerobic digestion (AD) of food waste diverts organic waste from landfills, generates sustainable baseload energy, and potentially an ecotoxic ammonia-rich digestate that requires post-treatment. Successful application of algal-based technology to treating high-ammonia AD effluents can be achieved by freshwater dilution. However, dilution of high-strength effluents with freshwater is currently unsustainable. Here, the feasibility of growing Chlorella sp. on the effluent of food waste anaerobic digestate with high ammonia content under recycling of the treated effluent was investigated for nutrient management and biomass production. The performance of the Chlorella sp. cultivated in repeated batch with effluent recycling (BR) and without recycling (BNR) was compared with repeated fed-batch mode with recycling (FR) and without recycling (FNR). Maximum cell density (6.1 × 107 cells mL−1) corresponding to the highest chlorophyll a (23.3 ± 1.3 mg L−1) content was found in the FNR. Ammonia removal rates were not significantly different among all tested treatments. In all treatments, the analysis of the operating efficiency of PSII photochemistry (Fq′/Fm′) of the culture showed values > 0.5, indicating cells were not subjected to physiological stress. Harvested Chlorella biomass composition showed no variation in the contents of total protein, carbohydrate, and lipids. Turbidity increase in cultures with effluent recycling versus without recycling was negligible (5%), demonstrating the suitability of effluent recycling in the microalgae-based treatment of high-strength ammonia food waste digestate

Bio-prospecting and growth of macroalgae on anaerobic digestion piggery effluent (ADPE)

Anaerobic digestion piggery effluent (ADPE) has high ammonium content (toxic to most organisms) and is very turbid. The environmental consequences of high productivity piggeries is significant and can result in negative environmental impacts, hence bioremediation techniques (in particular using macroalgae) are therefore of great interest. In this study, we evaluated the growth potential of several locally isolated macroalgae in ADPE under outdoor climatic conditions and investigated their nutrient removal rates and biochemical composition. A consortium of two macroalgae, Rhizoclonium sp. and Ulothrix sp. was isolated and could efficiently grow in the ADPE with concentration of up to 248.4 mg NH3. N L-1. Macroalgal consortium growth could not be maintained at higher ADPE concentration. Maximum ammonium removal rate (30.6 ± 6.50 mg NH4+-NL-1d-1) was achieved at ADPE concentration equivalent to 248.4 mgNH4+-NL-1. Mean biomass productivity of 31.1 ± 1.14 g AFDW m-2d-1 was attained. Total carbohydrate and protein contents ranged from between 42.8-54.8 and 43.4-45.0% (ash-free dry weight), respectively, while total lipid content was very low. Our findings highlight the potential use and promise of Rhizoclonium and Ulothrix sp. consortium for the bioremediation of ADPE and biomass production. To the best of author’s knowledge, this is the first study evaluating the potential of using macroalgae to treat ADPE. While there is a need for further optimisation, successful macro algae growth on ADPE indicates the potential of using these organisms for not only treating ADPE but also as a potential source of animal feed or bioenergy production

Viability of combining microalgae and macroalgae cultures for treating anaerobically digested piggery effluent

Algal phytoremediation represents a practical green solution for treating anaerobically digested piggery effluent (ADPE). The potential and viability of combining microalgae and macroalgae cultivation for the efficient treatment of ADPE were evaluated in this study. Bioprospecting the ability of different locally isolated macroalgae species illustrated the potential of Cladophora sp. to successfully grow and treat ADPE with up to 150 mg/L NH4+ with a biomass productivity of (0.13 ± 0.02) g/(L·day) and ammonium removal rate of (10.23 ± 0.18) mg/(L·day) NH4+. When grown by itself, the microalgae consortium used in this study consisting of Chlorella sp. and Scenedesmus sp. was found to grow and treat undiluted ADPE (up to 525 mg/L NH4+) with an average ammonium removal rate of 25 mg/(L·day) NH4+ and biomass productivity of (0.012 ± 0.0001) g/(L·day). Nevertheless, when combined together, despite the different cultivation systems (attached and non-attached) evaluated, microalgae and macroalgae were unable to co-exist together and treat ADPE as their respective growth were inversely related to each other due to direct competition for nutrients and available resources as well as the negative physical interaction between both algal groups