Simultaneous Biomass Production Research Articles

Sequential two-stage cultivation system using novel microalga consortia for treatment of municipal wastewater and simultaneous biomass production: Sustainable environmental management

Monoculture-based microalgae cultivation systems to treat wastewater are well-reported. Despite that, this method has some limitations in terms of nutrient removal potential, environment adaptation, and low biomass productivity. Conversely, microalgae co-cultivation and a two-stage sequential cultivation system (TSSCS) recently emerged as a promising approach to improve the treatment process and biomass productivity through better adaptation to the environment. However, no outdoor large-scale experiments were reported using this approach which hinders the viability of the process. Thus, in the present study, a sequential two-stage large-scale outdoor novel microalgae consortia experiment was developed. In first stage consortia-assisted sequential cultivation, two ratios of Tetraselmis indica (TS) and one ratio of Picochlorum sp. (PC) (2 TS:1 PC) were cultivated in a 1000-L pond containing 75%-municipal wastewater (MWW) + 25%-ASN-III, while in the second stage, 2 PC:1 TS was cultivated in two different ponds, and each containing 375-L 2 TS:1 PC-treated water + 375-L ASN-III. Outdoor parameters and nutrient removal efficiency (NRE), biomass, and biomolecule productivity such as lipid, photosynthetic pigments, astaxanthin, and β-carotene were quantified, and cost analysis was performed. At the end of the first and second stages, 2 TS:1 PC and 2 PC:1 TS showed maximum NRE of COD (68.71 and 86.40%), TN (66.98 and 94.73%), and TP (82.70 and 94.36%), respectively. Moreover, 2 TS:1 PC and 2 PC:1 TS Pond 1 and 2 produced maximum dry biomass production; 2.41 and ∼2.54 g/L contained lipid content; 36.89 and 34.90% that have 86.50 and 55.79% FAME content respectively. Similarly, 2 TS:1 PC and 2 PC:1 TS biomass exhibited valuable pigments production of astaxanthin i.e., 0.56 and 0.35 mg/g, and β-carotene; 4.65 and 2.82 mg/g, respectively. The cost analysis suggested that only microalgal-based MWW treatment was unfeasible, while valorization of produced biomass into co-products could offset the operation costs and could allow the option for the microalgal-based sustainable approach for the treatment of MWW and recovery of valuable resources.

Hydrothermal liquefaction of swine wastewater-cultivated Chlorella sorokiniana SU-1 biomass for sustainable biofuel production

The environmental impact of fossil fuel consumption has shifted the focus of research toward biomass and bioenergy. Renewable biomass, such as microalgae, has several benefits, including growth in wastewater, sequestration of carbon dioxide, economic feasibility, and environmental friendliness. This study investigated the feasibility of using Chlorella sorokiniana SU-1 biomass cultivated on a swine-amended medium as a renewable feedstock to produce biocrude oil. Microalgal cultivation under optimal conditions of 50 % swine wastewater (SW), inoculum sizes of 1 g/L, CO2 concentration of 2 %, and light intensity of 300 μmol m−2 s−1 obtained a high biomass concentration (6.53 g/L), biochemical production (56.65 % carbohydrate content, 33.5 % protein content, and 4.35 % lipid content) and wastewater treatment performance [92.29 % chemical oxygen demand (COD) removal, 93.7 % total phosphorus (TP) removal, and 95.64 % ammonia removal]. Subsequently, hydrothermal liquefaction (HTL) of the obtained microalgal biomass achieved a 29.45 % biocrude oil yield with a composition of 34.3 % esters, 23.5 % hydrocarbons, 5.14 % aldehydes, 7.54 % furans, and 11.1 % phenolic derivatives, making it a promising choice for biofuel production. Thus, the findings confirmed that C. sorokiniana SU-1 could be effectively utilized for the phycoremediation of SW with simultaneous biomass production as a renewable feedstock for biocrude oil production.

Simultaneous production of algal biomass and lipid by heterotrophic cultivation of linoleic acid-rich oleaginous microalga Chlorella sorokiniana using high acetate dosage

The low-cost carbon source, acetate, was utilized to feed a linoleic acid-rich Chlorella sorokiniana for microalgal biomass and lipid accumulation. Remarkably high tolerance capability to high acetate dosage up to 30 g/L was observed, with heterotrophy being the preferred trophic mode for algal growth and lipogenesis when supplemented 20 g/L acetate. Transcriptome analysis revealed a marked activation of pathways involved in acetate bioconversion and lipogenesis upon exposure to high-level of acetate. However, the enhancement of photorespiration inhibited photosynthesis, which ultimately led to a decrease in biomass and lipid under mixotrophy. Heterotrophic acetate-feeding generated more superior amino acid profiling of algal biomass and a predominant linoleic acid content (50 %). Heterotrophic repeat fed-batch strategy in 5 L fermenter significantly increased the growth performance and lipid titer, with the highest levels achieved being 23.4 g/L and 7.0 g/L, respectively. This work provides a viable approach for bio-products production through acetate-based heterotrophic algal cultivation.

Simultaneous production of dry solid biomass and liquid extract from Sorghum bicolor using liquefied ammonia

Energy-consuming processes should be avoided while separating biomass components. This study investigated the dewatering and extraction of components from Sorghum bicolor silage using liquefied NH3 (NH3(l)). Using a plug-flow-type reactor, NH3(l) was passed through the specimen at 20 °C and 0.85 MPa. When the NH3/wet sample weight was 4.7, a 31.0 wt% dry ammonia-treated sample (AT) was obtained as an extract, achieving a 96.5 wt% dewatering ratio. Glucose, xylose, and an acid-insoluble fraction were retained in the AT, whereas lactic and acetic acids were separated as an extract. Crystalline cellulose was transformed, and the increase in glucose and xylose yields from the enzymatic hydrolysis of the AT was similar levels to those from sulfuric acid hydrolysis. Therefore, NH3(l) treatment can dewater S. bicolor silage without severe pretreatment. In addition, it can be used in biofuel and chemical production using enzymatically degradable ATs from which organic acids are separated as extracts.

Purple acid phosphatase promoted hydrolysis of organophosphate pesticides in microalgae

When organophosphate pesticides (OPs) are not used and handled in accordance with the current rules and standards, it results in serious threats to the aquatic environment and human health. Phaeodactylum tricornutum is a prospective microalgae-based system for pollutant removal and carbon sequestration. Genetically engineered P. tricornutum, designated as the OE line (endogenously expressing purple acid phosphatase 1 [PAP1]), can utilize organic phosphorus for cellular metabolism. However, the competencies and mechanisms of the microalgae-based system (namely the OE line of P. tricornutum) for metabolizing OPs remain to be addressed. In this study, the OE line exhibited the effective biodegradation competencies of 72.12% and 68.2% for 30 mg L−1 of dichlorvos and 50 mg L−1 of glyphosate, accompanied by synergistic accumulations of biomass (0.91 and 0.95 g L−1) and lipids (32.71% and 32.08%), respectively. Furthermore, the biodiesel properties of the lipids from the OE line manifested a high potential as an alternative feedstock for microalgae-based biofuel production. A plausible mechanism of OPs biodegraded by overexpressed PAP1 is that sufficient inorganic P for adenosine triphosphate and concurrent carbon flux for the reduced form of nicotinamide adenine dinucleotide phosphate biosynthesis, which improved the OP tolerance and biodegradation competencies by regulating the antioxidant system, delaying programmed cell death and accumulating lipids via the upregulation of related genes. To sum up, this study demonstrates a potential strategy using a genetically engineered strain of P. tricornutum to remove high concentrations of OPs with the simultaneous production of biomass and biofuels, which might provide novel insights for microalgae-based pollutant biodegradation.

Simultaneous production of high-value lipids in Schizochytrium sp. by synergism of chemical modulators.

The study focuses on the simultaneous improvement of biomass, lipid, and docosahexaenoic acid (DHA) productivities in a single reactor using modulator control strategies. The efficacy of three different biochemical modulators, sesamol (Ses), 6-benzylaminopurine (6-BAP), and ethylenediaminetetraacetic acid (EDTA), as potential stimulants in augmenting the biomass, lipid, and DHA production of Schizochytrium sp. MTCC 5890 was elucidated. After 48h of cultivation, among tested modulators, the individual supplementation of 6-BAP and Ses showed improvement in biomass, lipid, and DHA accumulation by 28.2%, 56.1%, and 87.2% and 21.7%, 47.9%, and 91%, respectively, over the non-supplemented group. In addition, the cooperative effect of selected concentrations, i.e., 10 mgL-1 6-BAP and 200 mgL-1 Ses, further increased the productivities of biomass of 13.5 gL-1d-1 ± 0.66, lipid of 7.4 gL-1d-1 ± 0.69, and DHA of 3.2 gL-1d-1 ± 1.09 representing 8%, 39%, and 69% increase over the individual addition of 6-BAP or Ses, respectively, in batch culture. Supplementation with 6-BAP + Ses at 12h of time point eventually increased the lipid yield to 15.6 ± 0.42 gL-1 from 7.88 ± 0.31 gL-1 (control) and DHA yield to 6.4 ± 0.11 gL-1 from 2.23 ± 0.09 gL-1 (control), respectively. Furthermore, the process was optimized in continuous culture supplemented with 6-BAP + Ses for enhanced productivities. Continuous culture resulted in maximum biomass (2.04 ± 1.12 gL-1day-1), lipid (1.0 ± 0.73 gL-1day-1), and DHA (0.386 ± 0.22 gL-1day-1) productivities, which were higher as compared with the batch and fed-batch processes by 26 ± 1.21%, 22 ± 1.01%, and 21 ± 0.98% and 24 ± 0.45%, 16 ± 0.38%, and 14 ± 0.12%, respectively. This work represents the potential application of the combined effect of modulators for the simultaneous enhancement of biomass production and lipid and DHA productivities. KEY POINTS: • The cumulative study of 6-BAP and sesamol proved to be more efficient in the simultaneous production of biomass, lipid, and DHA in a single reactor. • Addition of a combination of 6-BAP + Ses remarkably increased the biomass, lipid, and DHA productivities in tandem in continuous culture.

Simultaneous Biomass Production, Carbohydrate Accumulation, and Contaminants Removal Using Malting Wastewater in Microalgae Cultivation

Simultaneous Biomass Production, Carbohydrate Accumulation, and Contaminants Removal Using Malting Wastewater in Microalgae Cultivation

Co-production of high density biomass and high-value compounds via two-stage cultivation of Chlorella vulgaris using light intensity and a combination of salt stressors

In this study, the effects of combined stress factors involving light intensity and salinity (NaCl, MgCl2, CaCl2, and their combinations) on the two-stage cultivation of Chlorella vulgaris for simultaneous production of biomass and high-value products, were investigated. The two-stage strategies comprised a 25-day vegetative stage in BG11 medium, followed by a 15-day combined stress stage. During salt stress conditions, the addition of 15 g L−1 CaCl2 or 7.5 g L−1 MgCl2 / 7.5 g L−1 CaCl2 mixture with 140 µmol m−2 s−1 light intensity significantly promoted the growth of C. vulgaris achieving maximum biomass productivity of 50.50 ± 0.50 and 50.25 ± 3.25 mg L−1 d−1, respectively. Cultivation of C. vulgaris in a medium containing 7.5 g L−1 NaCl/ 7.5 g L−1 CaCl2 had remarkably increased the lipid content (31.15 ± 1.18%) and lipid productivity (14.55 ± 1.48 mg L−1 d−1). The saturated fatty acids (SFAs) at 39.52–59.29%, monounsaturated fatty acids (MUFAs) at 27.16–35.47%, and polyunsaturated fatty acids (PUFAs) at 7.18–29.97%, were obtained with palmitic (C16:0), oleic (C18:1), stearic (C18:0), and linolenic (C18:3) acids as predominant fatty acids. Cultures supplemented with 5 g L−1 NaCl / 5 g L−1 MgCl2 / 5 g L−1 CaCl2 and high light intensity exposure attained consistently high carbohydrate content (52.71 ± 2.50%). The combination of 7.5 g L−1 NaCl / 7.5 g L−1 MgCl2 also resulted in a marked increase in the protein content (35.32 ± 2.20%) and total carotenoids (0.31 ± 0.03 μg mL−1) as compared to the Controls. The highest antioxidant activity (86.16%) was achieved with a 7.5 g L−1 NaCl / 7.5 g L−1 CaCl2 combination in the growth stage. The antioxidant activities were attributed to the presence of phenolics, flavonoids, and tannins due to the stressed conditions. One of the key benefits of using a combined stress strategy in this study is that if one factor has a low impact on enhancing target metabolites, other factors can compensate.

Physiological and molecular insights into adaptive evolution of the marine model diatom Phaeodactylum tricornutum under low-pH stress

The direct use of industrial flue gas in microalgae production is desired for mitigating CO2 emissions, but the low pH resulting from the inflow of acidic gases (mainly CO2, NOx, and SOx) imposes detrimental effects on microalgal growth and is considered the main technical challenge for simultaneous biomass production and CO2 sequestration. In this study, we investigated the adaptive responses of the model marine diatom Phaeodactylum tricornutum to acidic stress at pH 6.0. Gradual changes in the ratio of morphotypes, chlorophyll content, and photosynthetic efficiency were observed as a result of adaptive laboratory evolution (ALE) under constant acidic stress. The evolved strains showed a significant increase in growth rate in acidic conditions after ALE, and phenotypic characterization demonstrated a stable trait of acid tolerance with an average increase in growth by 110.4%, 46.1%, and 27.5% at pH 5.5, 6.0, and 6.5, respectively compared with the parental wild-type strain. Furthermore, RNA sequencing and whole-genome re-sequencing analyses revealed that core pathways, including photosynthesis, pH regulation/ion transport, and carbohydrate and fatty acid metabolism, were upregulated across all three evolved strains, though they exhibited different evolutionary trajectories. This study demonstrated the feasibility of recovering photosynthetic capability after acidic stress in the marine diatom P. tricornutum through ALE and provided molecular data to reveal essential alterations in genetic regulations that could enable cells to tolerate low environmental pH.

Growth Parameters of Various Green Microalgae Species in Effluent from Biogas Reactors: The Importance of Effluent Concentration.

The use of liquid waste as a feedstock for cultivation of microalgae can reduce water and nutrient costs and can also be used to treat wastewater with simultaneous production of biomass and valuable products. This study applied strategies to treat diluted anaerobic digester effluent (ADE) as a residue of biogas reactors with moderate (87 ± 0.6 mg L-1; 10% ADE) and elevated NH4+-N levels (175 ± 1.1 mg L-1; 20% ADE). The effect of ADE dilution on the acclimatization of various microalgae was studied based on the analysis of the growth and productivity of the tested green algae. Two species of the genus Chlorella showed robust growth in the 10-20% ADE (with a maximum total weight of 3.26 ± 0.18 g L-1 for C. vulgaris and 2.81 ± 0.10 g L-1 for C. sorokiniana). The use of 10% ADE made it possible to cultivate the strains of the family Scenedesmaceae more effectively than the use of 20% ADE. The growth of Neochloris sp. in ADE was the lowest compared to other microalgal strains. The results of this study demonstrated the feasibility of introducing individual green microalgae into the processes of nutrient recovery from ADE to obtain biomass with a high protein content.

Bioremediation strategies of palm oil mill effluent and landfill leachate using microalgae cultivation: An approach contributing towards environmental sustainability

Palm oil mill effluent (POME) is defined as the wastewater that contains high concentrations of organics, nutrients and oil and grease generated from the production process of palm oil. Therefore, proper discharge and management of POME is important to avoid deleterious impact on the environment. In fact, solid waste generation is a precursor for its disposal issues as most of the solid waste generated in developing nations is dumped into landfills. This has led to the threat posed by the generation of landfill leachate (LL). LL is a complex dark coloured liquid consisting of organic matter, inorganic substances, trace elements and xenobiotics. Hence, it is essential to effectively treat the landfill leachate before discharging it to avoid contamination of soil, surface & groundwater bodies. Conventional treatment methods comprises of physical, biological and chemical treatment, however, microalgal-based treatment could also be incorporated. Furthermore, with the benefits offered by microalgae in valorisation, the application of microalgae in POME and leachate treatment as well as biofuel production, is considerably viable. This paper provides an acumen of the microalgae-based treatment of POME and LL, integrated with biofuel production in a systematic and critical manner. The pollutants assimilation from wastewater and CO2 biosequestration are discussed for environmental protection. Cultivation systems for wastewater treatment with simultaneous biomass production and its valorisation, are summarised. The study aims to provide insight to industrial stakeholders on economically viable and environmentally sustainable treatment of wastewaters using microalgae, and eventually contributing to the circular bioeconomy and environmental sustainability.

Cost-effective treatment of sewage wastewater using microalgae Chlorella vulgaris and its application as bio-fertilizer

The present study lays an emphasis on microalgae-based treatment of sewage wastewater using Chlorella vulgaris to remove toxic pollutants and nutrients from the wastewater, making it safely dischargeable and reusable as bio-fertilizer, with simultaneous biomass and lipid production. The sewage treatment experiment was carried out in a 50 L capacity outdoor open syntax tank. The results exhibited the survival efficiency of C. vulgaris in sewage wastewater generating 0.67 g/L biomass and 0.26 g/L lipid yields. Crucial environmental factors like light intensity and temperatures have played a key role in biomass growth, lipid accumulation and nutrient removal efficiencies of C. vulgaris. The concentrations of significant nutrients like nitrates, COD and BOD were reduced up to 93%, 95% and 92% respectively. Other nutrients and parameters were removed up to 90% on an average. The treated sewage wastewater was then supplied as a bio-fertilizer to grow Solanum lycopersicum (tomato) plants as a comparative to chemical fertilizer grown plants. The results obtained from the comparative analyses showed that the tomato plant grown with treated sewage wastewater showed efficient growth and productivities as good as the chemical fertilizer aided yields. This study proved that sewage can be a successful replacement to the chemical fertilizers. The details are ornately discussed inside the paper.

Development of chloroplast engineering tools for Asterarcys sp.: A resilient scenedesmaceae microalga

The vast biodiversity of algae presents an opportunity to discover novel microalgae with diverse phenotypes having a commercial application. Asterarcys sp. is a resilient microalga demonstrating tolerance to elevated light intensity and nitric oxide concentrations with simultaneous production of high biomass and lipid content. The development of genetic tools for this microalga will further widen its biotechnological potential. We report the construction of a modular chloroplast vector as well as the establishment of a chloroplast transformation method for this microalga using the endogenous genetic sequences. The endogenous promoters, located upstream of psbA and atpA genes were isolated using the recently published chloroplast genome and were functionally validated in E. coli. Similarly, the homology arms of the vector were isolated by genome walking from the rrnS-rrnL operon using the chloroplast genome sequence of Asterarcys sp. These genetic elements were assembled to construct a species-specific vector with codon optimized aadA gene as the selectable marker. To the best of our knowledge, this is the first report of chloroplast engineering of a microalga belonging to the Scenedesmaceae.

Towards high-level protein, beta-carotene, and lutein production from Chlorella sorokiniana using aminobutyric acid and pseudo seawater

Microalgae produced lipids, pigments, lutein, and valuable chemicals under stressful conditions, making them as attractive feedstock for biorefineries. However, high cell density culture of microalgae in harsh condition using seawater is still a challenge. In this study, we used aminobutyric acid (GABA) from an in vitro biotransformation of monosodium glutamate (MSG) to alleviate salinity stress in Chlorella sorokiniana (Cs). Initially, Chlorophyll a/b content was suppressed under the stress of 20 g/L sodium chloride (NaCl), leading to an extreme decline in protein and pigment accumulation. While the biomass and protein of Cs cultured in 10 g/L NaCl reached 3.44 g/L and 1.14 g/L with 5 mM GABA, with 56.3% and 171% increase compared to control. The optimal conditions were 10 mM GABA and 20 g/L NaCl in modified BG11 medium, with a biomass, protein, lutein and β-carotene content of 4.56 g/L, 2.07 g/L, 24 mg/L and 27.48 mg/L, respectively. Finally, protein from Cs was used as a prebiotic for cultivating Escherichia coli Nissle 1917 (EcN) and Lactobacillus rhamnosus ZY (LGG). We provided an effective and sustainable approach for the simultaneous production of biomass and high-end products by microalgae using GABA and seawater for the first time.

Almond hulls waste valorization towards sustainable agricultural development: Production of pectin, phenolics, pullulan, and single cell protein

This research aimed to valorize almond hulls based on a zero-waste strategy towards sustainable agricultural developments for the recovery and production of valuable compounds. For this purpose, the potential to produce four products, including pectin (AHP), phenolic compounds (AHPC), pullulan (PUL), and single-cell protein (SCP), was examined. The acidic extraction factors were optimized using a Box-Behnken design for the simultaneous extraction of AHP and AHPC, and the obtained results showed that the maximum AHP (26.32% w/w) and AHPC (6.97% w/w) yields were achieved at 90 °C, pH of 1.4, 58.65 min, and liquid–solid ratio (LSR) of 20.13 v/w as the optimum point. In the next step, the solid residues that remained from the AHP and AHPC extraction process (PESR) were treated with cellulase enzyme and ultrasound and were used for simultaneous microbial production of PUL (34.29–24.56 g/L) and biomass containing SCP (19.31–13.44% w/w). Furthermore, the obtained results showed that AHP was low methylated (26.40%), rich in galacturonic acid (67.88%), and high in molecular weight (595.299 kDa). Also, the investigations of structural properties of AHP and PUL confirmed the presence of chemical structures of these polysaccharides in the formed supernatants. In addition, the AHPC showed considerable antioxidant activity compared with ascorbic acid (ASC) and BHA.

Design and development of mini-photobioreactor system for strategic high throughput selection of optimum microalgae-wastewater combination

This study establishes an innovative and economic mini-photobioreactor system (mPBR) providing an optimum microalgae-wastewater screening tool. This study enables the effectiveness of microalgae in wastewater treatment by enhancing its productivity through improved operating conditions such as controlled light, temperature, and agitation. This was achieved by designing 1-L photobioreactor with multiple mPBR to enable the screening of nine microalgal cultures (native and procured) under similar operating conditions (Light-11,000 Lux; Aeration - 1.5 LPM; Temperature- 25 ± 2 °C) using three wastewaters [sewage treatment plant (STP), dairy processing industry (DWW), and slaughterhouse processing unit (SWW)]. The native cultures outperformed for nutrient recovery with best treatment in PA4 accounting 45–72% sCOD removal and, 90–98% NO3−-N, NH4+-N, and PO43−-P removal, with simultaneous biomass production of 1.7–2.3 gL−1. To conclude there was up to 31% increase in the microalgal biomass production, lowering incubation time from earlier reported 12 days in a stationary flask to 3 days in the mPBR.

Sustainable cultivation of Haematococcus pluvialis and Chromochloris zofingiensis for the production of astaxanthin and co‐products

AbstractLarge‐scale cultivation of microalgae for the production of high‐value compounds raises concerns on sustainability due to intense consumption of water resources. Use of wastewater for microalgae cultivation is considered a promising alternative, because it not only reduces water consumption, but also provides nutrients required for microalgae growth. In the present study, Haematococcus pluvialis and Chromochloris zofingiensis were cultivated in synthetic dairy wastewater (DWW) to identify the potential of developing high‐value product first biorefineries, with astaxanthin as the main product. H. pluvialis and C. zofingiensis cultivated in DWW achieved biomass concentrations of 0.55 ± 0.01 and 0.65 ± 0.01 g/L, respectively. Astaxanthin contents of 2.1 ± 0.1% and 0.4 ± 0.1% were observed in H. pluvialis and C. zofingiensis grown in DWW. Minimum freshwater consumption for cultivation was 69.93 L/gastaxanthin in control growth media, which could be eliminated by cultivation of microalgae in DWW. COD, TN, and TP removal efficiencies were in the range of 94%–96%, 79%–81%, and 57%–79%, respectively, indicating capability for simultaneous biomass production and phycoremediation. Presence of carbohydrates and lipids in residual biomass suggested the applicability as feedstock for biorefining. Potential avenues to integrate wastewater treatment, astaxanthin production, and valorization of residual biomass were discussed in context of high‐value product first biorefineries.

Mixotrophic Cultivation of Microalgae in Cassava Processing Wastewater for Simultaneous Treatment and Production of Lipid-Rich Biomass

Cassava processing wastewater (CPW) is a highly polluting, liquid residue of cassava processing, usually discarded or treated anaerobically. However, it can serve as a low-cost culture medium for microalgae. After a preliminary evaluation of the growth of 10 microalgal strains in diluted CPW, the microalgae Haematococcus pluvialis SAG 34−1b and Neochloris (Ettlia) oleoabundans UTEX 1185 were selected for cultivation in CPW without a supply of additional nutrients and evaluated for their growth, lipid production, and nutrients removal. Maximal biomass concentrations of 1.79 g·L−1 for H. pluvialis and 3.18 g·L−1 for N. oleoabundans were achieved with 25% CPW medium on the 13th day of growth. The algae H. pluvialis and N. oleoabundans removed 60.80 and 69.16% of the chemical oxygen demand, 51.06 and 58.19% of total nitrate, and 54.68 and 69.84% of phosphate, respectively. On average, lipid productivities reached 0.018 and 0.041 g·L−1 day−1 for H. pluvialis and N. oleoabundans, respectively. Therefore, cultivating these microalgae in diluted CPW is a promising treatment for cassava wastewater with simultaneous valuable biomass production.

Integrating anaerobic digestion and microalgae cultivation for dairy wastewater treatment and potential biochemicals production from the harvested microalgal biomass

Utilizing wastewaters as feedstock for microalgal cultivation has the dual benefits of water-saving and low nutrient costs, with simultaneous remediation of pollutants and generation of value-added biochemical products. This study employed two different strategies to treat raw dairy wastewaters with moderate and high chemical oxygen demand (COD) levels. For moderate-COD dairy wastewater, the wastewater was directly utilized as feedstock for algal cultivation, in which the effects of wastewater dilution ratios and algal inoculum sizes were investigated. The results show that the microalga strain used (Chlorella sorokiniana SU-1) was capable of obtaining a high biomass concentration of 3.2 ± 0.1 g/L, accompanied by 86.8 ± 6%, 94.6 ± 3%, and 80.7 ± 1%, removal of COD, total phosphorus (TP) and total nitrogen (TN), respectively. Meanwhile, the obtained microalgal biomass has lipids content of up to 12.0 ± 0.7% at a wastewater dilution ratio of 50% and an inoculum size of 2 g/L. For high-COD dairy wastewater, an integrated process of anaerobic digestion and microalgal phycoremediation was employed, and the effect of inoculum sizes was also studied. The inoculum size of 2 g/L gave highest biomass production of 4.25 ± 0.10 g/L with over 93.0 ± 2.0% removal of COD, TP, and TN. The harvested microalgal biomass has lipids and protein content of 12.5 ± 2.2% and 18.0 ± 2.2%, respectively. The present study demonstrated potential microalgal phycoremediation strategies for the efficient COD removal and nutrients recovery from dairy wastewater of different COD levels with simultaneous production of microalgal biomass which contains valuable components, such as protein and lipids.

Sustainable Cultivation of Desmodesmus armatus SAG276.4d using Leachate as a Growth Supplement for Simultaneous Biomass Production and CO2 Fixation

Microalgae cultivation has been identified to be highly beneficial for the production of valuable biomass. The recent worldwide interest is to cultivate microalgae in wastewater to replace the use of expensive commercial media. Microalgae can utilize nutrients from the wastewater for their biomass growth, which is useful as feedstock in many products. Interestingly, microalgae cultivation is also capable of reducing a greenhouse gas due to absorption of carbon dioxide (CO2) during photosynthesis. This study was conducted to study the growth of microalgae using leachate as a nutrient supplement. The scope of the research involved the cultivation of freshwater microalgae, Desmodesmus armatus, in the synthetics medium with various percentages of leachate under different light exposures. The growth parameters such as the specific growth rate, biomass productivity, and cell division time were used to evaluate the microalgae growth performance. The amount of CO2 absorbed during the cultivation was determined based on the total biomass production. The highest growth rate of 0.423/day was achieved using a 5% leachate medium under 12 h light duration, and the highest carbon fixation of 1.317 g CO2/L/day was calculated using a culture supplemented with 5% leachate with 24 h light period. The high presence of nutrients in the leachate has contributed to the growth of the microalgae; thus, it has great potential as an alternative growth medium to support biomass production and subsequently help to mitigate global warming.