Cultivation of Chlorella pyrenoidosa in anaerobic wastewater: The coupled effects of ammonium, temperature and pH conditions on lipids compositions

Coupling anaerobic co-digestion of winery waste and waste activated sludge with a microalgae process: Optimization of a semi-continuous system

Wine production represents one of the most important agro-industrial sectors in Italy. Wine lees are the most significant waste in the winery industry and have high disposal and storage costs and few applications within the circular economy. In this study, anaerobic digestion and a microalgae coupled process was studied in order to treat wine lees and waste activated sludge produced within the same facility, with the aim of producing energy and valuable microalgae biomass that could be processed to recover biofuel or biostimulant. Chlorella vulgaris was cultivated on liquid digestate in a semi-continuous system without biomass recirculation. The best growth and phytoremediation performance were achieved applying a hydraulic retention time (HRT) of 20 days with a stable dry weight, lipid and protein storage of 1.85 ± 0.02 g l-1, 33.48 ± 7.54 % and 57.85 ± 10.14 % respectively. Lipid characterization highlighted the potential use in high quality biodiesel production, according to EN14214 (<12 % v/v linolenic acid). The microalgae reactor's liquid output showed high removal of ammonia (95.72 ± 2.10 %), but low organic soluble matter reduction. Further semi-continuous process optimization was carried out by increasing the time between digestate feeding and biomass recovery at HRT 10. These operative changes avoided biomass wash-out and provided a stable phytoremediation of the digestate with 84.58 ± 4.02 % ammonia removal, 33.01 ± 1.44 % sCOD removal, 38.06 ± 2.65 % of polyphenols removal.

Combined zeolite-based ammonia slow-release and algae-yeast consortia to treat piggery wastewater: Improved nitrogen and carbon migration

Integration of zeolite-based ammonia adsorption and algae-yeast consortia was developed to remediate piggery wastewater (PW) containing high concentrations of total ammonia nitrogen (TAN) and total organic carbon (TOC). After optimizing the conditions of ammonia adsorption in the PW. Zeolite addition mitigated ammonia toxicity, allowing zeolites to gradually release ammonia while effectively attenuating algal oxidative stress caused by high TAN concentration. Coupling zeolite-based adsorption and yeast co-incubation further increased TOC degradation and available C/N ratio, thus improving biomass (4.51 g/L), oil yield (2.11 g/L), and nutrient removal (84.18%-99.14%). The integrated microalgae-based PW treatment exhibited higher carbon migration into biomass (46.14%) and reduced treatment costs than conventional approaches. Simultaneously, the lowest carbon migration to wastewater also meant the smallest carbon emission into water bodies. These findings demonstrate that this novel strategy can remove nutrients in raw PW effectively and produce high oil-rich biomass in a sustainable and environmentally-friendly manner.

Transition from synthetic to alternative media for microalgae cultivation: A critical review

In recent decades, microalgae have drawn attention as a most feasible alternative and sustainable feedstock for biofuel production. However, laboratory-scale and pilot-scale studies revealed that producing only biofuels through the microalgal route is economically unfeasible. The high cost of synthetic media is one concern, and low-cost alternative cultivation media would replace synthetic media to culture microalgae for economic benefit. This paper critically consolidated the advantages of alternative media over synthetic media for microalgae cultivation. A comparative analysis of the compositions of synthetic and alternative media was made to evaluate the potential use of alternative media in microalgae cultivation. Investigations on microalgae cultivation using alternative media derived from different waste materials, such as domestic, farm, agricultural, industrial, etc., are highlighted. Vermiwash is another alternative media that contains essential micro and macronutrients required for the cultivation of microalgae. Two prime techniques, such as mix-waste culture media and recycling culture media, may provide more economic benefit for the large-scale production of microalgae.

Assessing the potential of Chlorella sp. phycoremediation liquid digestates from brewery wastes mixture integrated with bioproduct production

Digestates from different anaerobic digesters are promising substrates for microalgal culture, leading to effective wastewater treatment and the production of microalgal biomass. However, further detailed research is needed before they can be used on a large scale. The aims of this study were to investigate the culture of Chlorella sp. in Digestate_M from anaerobic fermentation of brewer's grains and brewery wastewater (BWW) and to explore the potential use of the biomass produced under different experimental conditions, including diverse cultivation modes and dilution ratios. Cultivation in Digestate_M initiated from 10% (v/v) loading, with 20% BWW, obtained maximum biomass production, reaching 1.36 g L^-1 that was 0.27g L^-1 higher than 1.09 g L^-1 of BG11. In terms of Digestate_M remediation, the maximum removal of ammonia nitrogen (NH₄ ⁺-N), chemical oxygen demand, total nitrogen, and total phosphorus reached 98.20%, 89.98%, 86.98%, and 71.86%, respectively. The maximum lipid, carbohydrate, and protein contents were 41.60%, 32.44%, and 27.72%, respectively. The growth of Chlorella sp. may be inhibited when the Y(II)-F_v/F_m ratio is less than 0.4.

Anaerobic digestates grown oleaginous microalgae for pollutants removal and lipids production

Anaerobic digestates were potential mediums for cultivating oleaginous microalgae, but their various components brought uncertainties for aglal growth and lipids production. In this study, three microalgae strains were tested to grow on four typical anaerobic digestates. The results showed that anaerobic food wastewater was an optimal medium for C. pyrenoidosa and S. obliquus culture (N. oleoabundanst cannot survive), achieving the highest biomass (2.15-2.32 g L^-1) and lipids production (20.6-32.5 mg L^-1·d^-1). In contrast, three microalgae strains could grow suboptimally in anaerobic municipal (0.79-0.95 g L^-1) and toilet (0.92-1.40 g L^-1) wastewater, but showed poor performances in anaerobic swine wastewater. The growth of microalgae removed 40.9-63.4% of TOC, 83.7-96.3% of NH₄⁺-N and 70.3-89.4% of TP in the three ADs. In addition, it was unfortunately found that the lipids content and saturation degree in fatty acids significantly decreased in ADs with sufficient nutrients. It suggests that some measures should be taken to balance biomass, lipids production and quality for cultivating microalgae in anaerobic digestates.

Effects of light source and inter-species mixed culture on the growth of microalgae and bacteria for nutrient recycling and microalgae harvesting using black odorous water as the medium

To achieve the sustainable and effective removal efficiency of nutrients in black odorous water, light source, inter-species microalgae mixed culture, and the harvesting effect were all explored. The results showed that under a LED light source, the addition of interspecific soluble algal products (SAP) promoted the growth of Haematococcus pluvialis (H. pluvialis) M1, and its maximum specific growth rate was 1.76 times that of H. pluvialis cultivated alone. That was due to the hormesis effect between the two kinds of microalgae, the SAP produced by Scenedesmus could stimulate the growth of H. pluvialis. The algae and bacteria symbiotic system with black odorous water as the medium showed excellent performance to treat nutrients, where the concentration of ammonia nitrogen (NH₃-N) and total phosphorus (TP) (0.84, 0.23 mg/L) met the requirements of landscape water. The microbial diversity analysis revealed that the introduction of microalgae changed the dominant species of the bacterial community from Bacteroidota to Proteobacteria. Furthermore, timely microalgae harvesting could prevent water quality from deteriorating and was conducive to microalgae growth and resource recycling. The higher harvest efficiency (98.1%) of H. pluvialis was obtained when an inoculation size of 20% and 0.16 g/L FeCl₃ were provided.

Target of Rapamycin Regulates Photosynthesis and Cell Growth in Auxenochlorella pyrenoidosa

Auxenochlorella pyrenoidosa is an efficient photosynthetic microalga with autotrophic growth and reproduction, which has the advantages of rich nutrition and high protein content. Target of rapamycin (TOR) is a conserved protein kinase in eukaryotes both structurally and functionally, but little is known about the TOR signalling in Auxenochlorella pyrenoidosa. Here, we found a conserved ApTOR protein in Auxenochlorella pyrenoidosa, and the key components of TOR complex 1 (TORC1) were present, while the components RICTOR and SIN1 of the TORC2 were absent in Auxenochlorella pyrenoidosa. Drug sensitivity experiments showed that AZD8055 could effectively inhibit the growth of Auxenochlorella pyrenoidosa, whereas rapamycin, Torin1 and KU0063794 had no obvious effect on the growth of Auxenochlorella pyrenoidosaa. Transcriptome data results indicated that Auxenochlorella pyrenoidosa TOR (ApTOR) regulates various intracellular metabolism and signaling pathways in Auxenochlorella pyrenoidosa. Most genes related to chloroplast development and photosynthesis were significantly down-regulated under ApTOR inhibition by AZD8055. In addition, ApTOR was involved in regulating protein synthesis and catabolism by multiple metabolic pathways in Auxenochlorella pyrenoidosa. Importantly, the inhibition of ApTOR by AZD8055 disrupted the normal carbon and nitrogen metabolism, protein and fatty acid metabolism, and TCA cycle of Auxenochlorella pyrenoidosa cells, thus inhibiting the growth of Auxenochlorella pyrenoidosa. These RNA-seq results indicated that ApTOR plays important roles in photosynthesis, intracellular metabolism and cell growth, and provided some insights into the function of ApTOR in Auxenochlorella pyrenoidosa.

Isolation and screening of indigenous microalgae species for domestic and livestock wastewater treatment, biodiesel production, and carbon sequestration

The use of indigenous microalgae strains for locally generated domestic (DWW) and livestock wastewater (LWW) treatment is essential for effective and economical applications. Phototrophic microalgae-based biofuel production also contributes to carbon sequestration via CO₂ fixation. However, simultaneous consideration of both isolation and screening procedures for locally collected indigenous microalgae strains is not common in the literature. We aimed to isolate indigenous microalgae strains from locally collected samples on coastlines and islands in South Korea. Among five isolated strains, Chlorella sorokiniana JD1-1 was selected for DWW and LWW treatment due to its ability to grow in waste resources. This strain showed a higher specific growth rate in DWW than artificial growth medium (BG-11) with a range of 0.137-0.154 d^-1. During cultivation, 96.5%-97.1% of total nitrogen in DWW and 89.2% in LWW was removed. Over 99% of total phosphorus in DWW and 96.4% in LWW was also removed. Finally, isolated C. sorokiniana JD1-1 was able to fix CO₂ within a range of 0.0646-0.1043 g CO₂ L^-1 d^-1. These results support the domestic applications of carbon sequestration-efficient microalgae in the waste-to-energy nexus.

Integrated role of algae in the closed-loop circular economy of anaerobic digestion

Following the surging demand for sustainable biofuels, biogas production via anaerobic digestion (AD) presented itself as a solution for energy security, waste management, and greenhouse gas mitigation. Algal-based biorefinery platform serves an important role in the AD-based closed-loop circular economy. Other than using whole biomass of micro- and macroalgae as feedstock for biogas production, the integration of AD with other bio- or thermochemical conversion techniques can achieve complete valorization of biomass residue after processing or valuable compounds extraction. On the other hand, anaerobic digestate, the byproduct of AD processes can be used for microalgal cultivation for lipid and pigments accumulation, closing the loop of resource flow. Furthermore, algae and its consortium with bacteria or fungi can be employed for combined biogas upgrading and wastewater treatment. Innovative strategies have been developed to enhance biogas upgrading and pollutant removal performance as well as minimize O₂ and N₂ content in the upgraded biomethane.

Effect of Propofol Nanoemulsion on Brain Perilymph Metabolism Through Transforming Growth Factor β1/Extracellular Signal Regulated Kinase 5 (TGF-β1/ERK5) Signaling Pathway

Propofol takes part in the metabolism of perilymph in the brain. Propofol nanoemulsion can enhance the efficacy of drugs. This study explored how propofol modified by nanoemulsion inhibited the TGF-β1/ERK5 signaling pathway, thus affecting the brain. The role of perilymph metabolism, and its mechanism of action were also clarified. 40 SD rats of clean grade were separated into 4 groups, namely; control group, propofol, propofol nanoemulsion and TGF-β1/ERK5 inhibitor group. We observed the particle size and potential of propofol nanoemulsion, concentration of several groups of immune factors, inflammatory factors, TGF-β1, and ERK5 protein expression. Results from the laser particle size analyzer showed that the average particle size for the propofol nanoemulsion was 87.14 nm. The zeta potential was 0.391 mV, which was close to electrical neutrality. ELISA results showed that the concentrations of IgG, IgA, and lgM in the propofol group, propofol nanoemulsion group, and TGF-β1/ERK5 inhibitor group were evidently lower and the IgG, IgA, IgM concentration for the propofol nanoemulsion group. Moreover, the concentration was lower than that of other groups. ELISA test results showed that the concentrations of IL-12, IL-10, TNF-α, and IL-2 in the propofol group, propofol nanoemulsion group, and TGF-β1/ERK5 inhibitor group were obviously lower. The concentrations of IL-12, IL-10, TNF-α and IL-2 in the propofol nanoemulsion group were lower than those in the other groups (p < 0.05). These results exhibited that, the expression levels of TGF-β1 and ERK5 in the propofol group, propofol nanoemulsion group, and TGF-β1/ERK5 inhibitor group were evidently lower. TGF-β1 and ERK5 expression levels in the propofol nanoemulsion group was lower than in the other groups (p<0.05). Propofol nanoemulsion regulates the TGF-β1/ERK5 signaling pathway, inhibits its expression, reducing inflammation, increasing immune response, and promoting perilymph metabolism in the brain.

Nano-Albumin Particles Loaded with miR-20a Inhibitor Targeting Met Protein to Reverse Proliferation of Intestinal Cancer Cells

This study explored miR-20a’s role in intestinal cancer cells. SW480 cell line was divided into control group, agonist group, inhibitor group, and negative control group, followed by analysis of cell proliferation, apoptosis, Met, Bad, and Bcl-2 protein expressions. Results showed that miR-20a expression in the agonist group was the highest, followed by blank group and negative control group, and inhibitor group was lowest. S-phase and G2/M cell number from inhibitor group was lowest, and cell apoptosis rate was highest. However, the agonist group showed contrary changes. There was no difference in G0/G1 phase cell number among the four groups (P > 0.05). Moreover, the expressions of Bad, Bcl-2, Met, Wnt, β-catenin, and p-Wnt in inhibitor group were all lower, while the expressions in agonist group were all high (P < 0.05). S-phase and G2/M cell number in inhibitor group was lowest, while cell apoptosis was highest. The agonist group was opposite, with G0/G1 phase cells in each group showing no difference (P > 0.05). Wnt, β-catenin, and p-Wnt expressions were lowest in the inhibitor group, while the agonist group was opposite. These results together showed that the miR-20a directly targeted and regulated Met protein. Finally, the miR-20a inhibited intestinal cancer cell proliferation mainly through inhibiting Wnt/β-catenin signaling activity.

DNA Templated Silver Nanoclusters for Bioanalytical Applications: A Review

Due to their unique programmability, biocompatibility, photostability and high fluorescent quantum yield, DNA templated silver nanoclusters (DNA Ag NCs) have attracted increasing attention for bioanalytical application. This review summarizes the recent developments in fluorescence properties of DNA templated Ag NCs, as well as their applications in bioanalysis. Finally, we herein discuss some current challenges in bioanalytical applications, to promote developments of DNA Ag NCs in biochemical analysis.

Resveratrol Nanoparticles Suppresses Migration and Invasion of Renal Cell Carcinoma Cells by Inhibiting Matrix Metalloproteinase 2 Expression and Extracellular Signal-Regulated Kinase Pathway

The aim of this study was to examine the impact of Resveratrol nanoparticles on migration/invasion capacity of renal cell carcinoma (RCC) cells and its mechanism. Human RCC cells were exposed to dimethyl sulfoxide or gradient concentrations of Resveratrol nanoparticles respectively, and U0126 were also added in some experiments. We examined renal cell viability by MTT assay, and wound healing test and Transwell assays were used detect invasion and migration capability of RCC cells. We used Western blotting assay to analyze the protein levels in extracellular signal-regulated kinase (ERK) signaling. We also detected the enzymatic capacity of matrix metalloproteinase 2 (MMP-2) in cells by gelatin enzymatic profiling. Resveratrol nanoparticles treatment significantly suppressed cell viability to migrate and invade RCC cells in a dose-dependent manner. Also, notably were reduced MMP-2 activity and expression, and elevated TIMP-2 level were observed in RCC cells exposed with Resveratrol nanoparticles. Further, Resveratrol nanoparticles treatment significantly decreased only the expression of p-ERK1/2, but not p-p38 and p-JNK. Moreover, U0126, which is the ERK inhibitor, exerted similar role as Resveratrol nanoparticles did. Of note was that, combined use of U0126 and Resveratrol nanoparticles displayed a more intense suppression of MMP-2 activity and expression, and also the viability to migrate and invade the RCC cells, compared with Resveratrol nanoparticles treatment alone. The Resveratrol nanoparticles inhibited RCC cells migration and invasion by regulating MMP2 expression and ERK pathways.

Effective bioremediation of tobacco wastewater by microalgae at acidic pH for synergistic biomass and lipid accumulation

Tobacco wastewater is too difficult to decontaminate which poses a significant environmental problem due to the harmful and toxic components. Chlorella pyrenoidosa is a typical microalgal species with potential in removal of organic/inorganic pollutants and proves to be an ideal algal-based system for wastewater treatment. However, the strategy of tobacco related wastewater treatment using microalgae is in urgent need of development. In this study, C. pyrenoidosa was used to evaluate the removal efficiency of artificial tobacco wastewater. Under various solid-to-liquid (g/L) ratios, 1:1 ratio and acidic pH 5.0 were optimal for C. pyrenoidosa to grow with high performance of removal capacity to toxic pollutants (such as COD, NH3-N, nicotine, nitrosamines and heavy metals) with the alleviation of oxidative damage. Algal biomass could reach up to 540.24 mg/L. Furthermore, carbon flux of C. pyrenoidosa was reallocated from carbohydrate and protein biosynthesis to lipogenesis with a high lipid content of 268.60 mg/L at pH 5.0. Overall, this study demonstrates an efficient and sustainable strategy for tobacco wastewater treatment at acidic pH with the production of valuable microalgal products, which provides a promising biorefinery strategy for microalgal-based wastewater bioremediation.

Use of reverse osmosis reject from drinking water plant for microalgal biomass production

The present study evaluates the use of reverse osmosis (RO) reject, termed as ROR, for microalgal biomass production. The supplementation of ROR from two different sources, namely domestic RO unit (ROR1) and commercial-scale RO plant (ROR2), showed a synergistic effect on the growth and biochemical composition of Chlorella pyrenoidosa. Among the tested ROR1 doses, the highest biomass production (1.27±0.06 g L^-1) was observed with 25% ROR1 supplemented growth media. In contrast, the lipid content (28.85±3.13% of TS) in C. pyrenoidosa at 50% ROR1 dose was almost twice that in BG11 (positive control). Interestingly, the microalgae showed relatively higher biomass production (1.37±0.07 g L^-1) and higher lipid content (33.23±3.92% of TS) when 50% ROR2 was used in growth media. At the same time, the estimated carbohydrate and protein contents were 28.41±0.73 and 29.75±0.31% of TS, respectively. Furthermore, the lipid productivity (28.98±2.79 mg L^-1 d^-1) was relatively higher than the nutrient media (12.35±1.34 mg L^-1 d^-1). The present findings revealed that the RO reject from drinking water purifiers can efficiently be utilized for lipid-rich microalgal biomass production. Hence, the dependency on freshwater resources for mass scale microalgae cultivation through recycling of RO reject can be reduced.

Paradigm shift in algal biomass refinery and its challenges

Microalgae have been studied and tested for over 70 years. However, biodiesel, the prime target of the algal industry, has suffered from low competitiveness and current steps toward banning the internal combustion engine all over the world. Meanwhile, interest in reducing CO₂ emissions has grown as the world has witnessed disasters caused by global warming. In this situation, in order to maximize the benefits of the microalgal industry and surmount current limitations, new breakthroughs are being sought. First, drop-in fuel, mandatory for the aviation and maritime industries, has been discussed as a new product. Second, methods to secure stable and feasible outdoor cultivation focusing on CO₂ sequestration were investigated. Lastly, the need for an integrated refinery process to simultaneously produce multiple products has been discussed. While the merits of microalgae industry remain valid, further investigations into these new frontiers would put algal industry at the core of future bio-based economy.

Growth of Chlorella pyrenoidosa on different septic tank effluents from rural areas for lipids production and pollutants removal

Septic tank effluent from rural areas was an ideal medium for cultivating oleaginous microalgae. However, the characteristics of septic tank effluents varied greatly due to the different incoming wastewater, and bring uncertain risks for algal growth. In this study, an oleaginous microalgae was cultivated in septic effluents from different mixed wastewater. The results showed that the effluent from pure toilet wastewater was the best medium to achieve the highest biomass yield (1.68 g·L^-1) and productivity (154.6 mg·L^-1·d^-1). In contrast, the discharge of kitchen or laundry wastewater reduced the biomass production by 50.5-79.1%. That caused much lower lipids production in effluents from mixed wastewater regardless of its high lipids content and saturation degree. The results suggest that the discharge of kitchen or laundry wastewater bring risks for biomass and lipids production, and should be separated from the toilet wastewater before entering into septic tank.

Cultivation of Nostoc sp. LS04 in municipal wastewater for biodiesel production and their deoiled biomass cellular extracts as biostimulants for Lactuca sativa growth improvement

In this study, seven different cyanobacteria (LS01-LS07) were isolated from paddy field water and among them, the isolate LS04 was able to grow well on municipal wastewater. The LS04 isolate was identified as Nostoc sp. (designated as Nostoc sp. LS04) based on 16S rRNA gene sequence analysis. Strain LS04 grew well in 75% wastewater and had the greatest nutrients removal efficiency (81.02-95.17%). Strain LS04 obtained the higher biomass (1.31 ± 0.08 g L-1) and productivity of 131.33 ± 8.08 mg L-1 d-1. The lipid content and productivity of LS04 were 14.85 ± 0.86% (dry cell weight) and 19.46 ± 0.05 mg L-1 d-1, respectively. The high proportion of C16-C18 fatty acids found in the lipids of LS04 indicated the high suitability for biodiesel production. In addition, Nostoc sp. LS04 cellular extracts were potentially used as a biostimulant for Lactuca sativa cultivation. The foliar application of 60% LS04 cellular extracts showed the maximum shoot length, root length, fresh biomass, dry biomass, Chl a, Chl b and carotenoids in lettuce plants compared to control plants. Similarly, 60% of LS04 cellular extracts treatment improved the concentrations of macro and micronutrients, and biochemical compounds in the leaves. Therefore, these results reveal that the Nostoc sp. LS04 is a promising candidate for the nutrients removal from wastewater and their biomass is a potential resource for biodiesel production and biostimulant for sustainable crop production.

Mixotrophic Chlorella pyrenoidosa as cell factory for ultrahigh-efficient removal of ammonium from catalyzer wastewater with valuable algal biomass coproduction through short-time acclimation

To achieve ultrahigh-efficient ammonium removal and valuable biomass coproduction, Chlorella-mediated short-time acclimation was implemented in photo-fermentation. The results demonstrated short-time acclimation of mixotrophic Chlorella pyrenoidosa could significantly improve NH₄⁺ removal and biomass production in shake flasks. After acclimation through two batch cultures in 5-L photo-fermenter, the maximum NH₄⁺ removal rate (1,400 mg L^-1 d^-1) were achieved under high NH₄⁺ level (4,750 mg L^-1) in batch 3. In 50-L photo-fermenter, through one batch acclimated culture, the maximum NH₄⁺ removal rate (2,212 mg L^-1 d^-1) and biomass concentration (58.4 g L^-1) were achieved in batch 2, with the highest productivities of protein (5.56 g L^-1 d^-1) and total lipids (5.66 g L^-1 d^-1). The hypothetical pathway of nutrients assimilation in mixotrophic cells as cell factory was proposed with detailed discussion. This study provided a novel strategy for high-ammonium wastewater treatment without dilution, facilitating the algae-based "waste-to-treasure" bioconversion process for green manufacturing.

Nutrients recycling and biomass production from Chlorella pyrenoidosa culture using anaerobic food processing wastewater in a pilot-scale tubular photobioreactor

Microalgae cultivation in anaerobic food wastewater was a feasible way for high biomass production and nutrients recycling. In this study, Chlorella pyrenoidosa culture on anaerobic food wastewater was processed outdoors using a pilot-scale tubular photobioreactor. The microalgae showed rapid growth in different seasons, achieving high biomass production of 1.83-2.10 g L^-1 and specific growth rate of 0.73-1.59 d^-1. The biological contamination and dissolved oxygen were controlled at suitable levels for algal growth in the tubular photobioreactor. Lipids content in harvested biomass was 8.1-15.3% of dried weight, and the analysis in fatty acids revealed high quality with long carbon chain length and high saturation. Additionally, algal growth achieved effective pollutants purification from wastewater, removing 42.3-53.8% of COD_Cr, 82.6-88.7% of TN and 59.7-67.6% of TP. This study gave a successful application for scaled-up microalgae culture in anaerobic food processing wastewater for biodiesel production and wastewater purification.

The joint effect of ammonium and pH on the growth of Chlorella vulgaris and ammonium removal in artificial liquid digestate

Although ammonium containing digestate is an ideal alternative medium for microalgae cultivation, high ammonium or unfavorable pH may inhibit microalgal growth. In this study, the joint effect of ammonium and pH on the growth of C. vulgaris and nutrient removal in artificial digestate was investigated. Our results show that ammonium and pH both affected algal growth, but free ammonia (FA) was the main actual inhibitory factor. Algal specific growth rate presented a negative correlation with FA and their relationship was well fitted by a linear regression model. Microalgal growth was little affected below 36.8 mg L^-1 FA, while the obvious inhibition occurred at 184 mg L^-1 FA (EC₅₀), indicating a high tolerance to FA. Ammonium removal was well described by a first-order kinetics model. FA stress stimulated the production of extracellular organic matters (EOMs), which was good for microalgae adaptation but adverse to pollutant removal.

Biomass and Lipid Productivity by Two Algal Strains of Chlorella sorokiniana Grown in Hydrolysate of Water Hyacinth

Hydrolysate prepared from the chemical hydrolysis of water hyacinth biomass contains a high amount of solubilised carbohydrate and nutrients. This hydrolysate was utilised as a medium for the cultivation of two strains of Chlorella sorokiniana, isolated from a municipal wastewater treatment plant using two different media, i.e., BG-11 and Knop’s medium. Different light intensities, light–dark cycles, and various concentrations of external carbon sources (monosaccharides and inorganic carbon) were used to optimise the microalgal growth. For the accumulation of lipids and carbohydrates, the microalgal strains were transferred to nutrient amended medium (N-amended and P-amended). It was observed that the combined effect of glucose, inorganic carbon, and a 12:12 h light–dark cycle proved to be the optimum parameters for high biomass productivity (~200 mg/L/day). For Chlorella sorokiniana 1 (isolated from BG-11 medium), the maximum carbohydrate content (22%) was found in P-amended medium (N = 0 mg/L, P: 3 mg/L), whereas, high lipid content (17.3%) was recorded in N-amended medium (N = 5 mg/L, P = 0 mg/L). However, for Chlorella sorokiniana 2 (isolated from the Knop’s medium), both lipid (17%) and carbohydrate accumulation (12.3%) were found to be maximum in the N-amended medium. Chlorella sorokiniana 2 showed a high saturated lipid accumulation compared to other strains. Kinetic modelling of the lipid profile revealed that the production rate of fatty acids and their various constituents were species dependent under identical conditions.

Anaerobic digestate water for Chlorella pyrenoidosa cultivation and employed as co-substrate with cow dung and chicken manure for methane and hydrogen production: A closed loop approach

In rural India, unpleasant atmosphere, anthropogenic gas emission, air and soil pollution are caused due to disposal of livestock's wastes (cow dung and chicken waste) in open environment. This study provides zero emission concept for waste disposal and value addition of these wastes for renewable green energy production. In this study, biogas production was carried out with varying proportion of cow dung to chicken waste (1:0, 0:1, 1:1, 2:1, 1:2, 3:1 and 1:3) for duration of 40 days. Chlorella pyrenoidosa was cultivated from digestate water and used as co-substrate in digester in varying proportions (2:1:1, 2:1:2 and 2:1:3) to study its role on biogas distribution. The effect of pH, feedstock ratio, time and C/N ratio for biogas production were evaluated. The maximum methane and hydrogen yield was 68% (30th day) and 29% (10th day) for 2:1:2 ratio respectively. The slurry possessed nitrogen (1.7%), phosphate (0.8%) and potassium (0.4%) respectively.

Screening of the dominant Chlorella pyrenoidosa for biofilm attached culture and feed production while treating swine wastewater

This research 12 microalgal species were screened for biofilm attached culture in the treatment of anaerobically digested swine wastewater (ADSW). The influence of ADSW on biomass productivity and removal efficiencies were evaluated using biofilm attached culture with the selected Chlorella pyrenoidosa. The variation of nutritional components from algal cells were further analysed to evaluate the potential applications of C. pyrenoidosa. The results showed that C. pyrenoidosa had the highest tolerance to ADSW, and the highest removal efficiencies for wastewater pollutants were reached when cultured in 5 times diluted ADSW. These test conditions resulted in an algal cell biomass composed of 57.30% proteins, 14.87% extracellular polysaccharide, 3.08% crude fibre, 5.57% crude ash, 2.85% moisture. Amino acids in proteins contained 21.73% essential amino acids and the EAA/NEAA value was 0.64. The essential amino acid score indicates that the selected C. pyrenoidosa could be a good protein source for feed addition.

Bioprocessing of cultivated Chlorella pyrenoidosa on poultry excreta leachate to enhance algal biomolecule profile for resource recovery

The aim of this work was to study the cultivation of Chlorella pyrenoidosa on poultry excreta leachate to enhance the biochemical composition of algal biomass. The growth of microalgae was analyzed with different concentrations of poultry excreta leachate in BG-11 and distilled water. The biomolecules observed have high value in the form of carbohydrates (0.64 gL^-1), protein (1.02 gL^-1), chlorophyll (20 µg mL^-1) and lipid amount (0.49 gL^-1) with PEL _BG -25%. Biomass produced in PEL _BG -25% was also found to be 60% (2.5 gL^-1) higher than the BG-11 medium as a control (1.5gL^-1). Recovery of nutrients was observed with leachate wastewater concentration in terms of nitrate (84.2%), ammonium nitrogen (53.1%), and inorganic phosphate (96.2%). Hence, sustainability of microalgae cultivation in wastewater provides a new insight for resource utilization.

Removal of ofloxacin with biofuel production by oleaginous microalgae Scenedesmus obliquus

Microalgae-based technology is an environmental-friendly and cost-effective method for biofuel production and pollutants removal. In this study, Scenedesmus obliquus (S. obliquus) was cultured with varying concentrations of ofloxacin (OFL) in BG11 medium. In the algae-antibiotics culture system, S. obliquus could effectively remove OFL with a concentration of 10 mg/L; however, the removal efficiency was restricted under higher doses (20-320 mg/L). Meanwhile, the lipid content significantly increased by 21.10-49.63%, which was caused by carbon being converted from carbohydrate to lipid. The greatest lipid productivity (7.53 mg/L/d) occurred at an OFL concentration of 10 mg/L, which was approximately 1.5-fold greater than the control. Moreover, S. obliquus cultured with OFL was able to improve the biodiesel quality due to an increase of saturated fatty acids and a decrease of unsaturated fatty acids. This study demonstrates that an algae-antibiotics system is a promising solution to simultaneously achieve antibiotics removal and biofuel production.

High-yield production of biomass, protein and pigments by mixotrophic Chlorella pyrenoidosa through the bioconversion of high ammonium in wastewater

To achieve a high consumption rate of ammonium with biomass coproduction, the mixotroph Chlorella pyrenoidosa was cultivated in high ammonium-high salinity wastewater medium in this study. The initial cell density, glucose and ammonium concentrations, and light intensity were optimized in shake flasks. A 5-L fermenter with surrounding LED (Light Emitting Diode) and a 50-L fermenter with inlet LED were employed for batch and semicontinuous cultivation. The results demonstrated that the highest contents of protein (56.7% DW) and total pigments (4.48% DW) with productivities of 5.62 g L^-1 d^-1 and 0.55 mg L^-1 d^-1, respectively, were obtained in 5-L photofermenter, while the maximum NH₄⁺ consumption rate (1,800 mg L^-1 d^-1) and biomass yield (23.6 g L^-1) were achieved in 50-L photofermenter. This study developed a novel strategy to convert high ammonium in wastewater to high-protein algal biomass, facilitating wastewater bioremediation and nitrogen recycling utilization by the mixotroph C. pyrenoidosa in photofermentation.

Comprehensive Utilization of Marine Microalgae for Enhanced Co-Production of Multiple Compounds

Marine microalgae are regarded as potential feedstock because of their multiple valuable compounds, including lipids, pigments, carbohydrates, and proteins. Some of these compounds exhibit attractive bioactivities, such as carotenoids, ω-3 polyunsaturated fatty acids, polysaccharides, and peptides. However, the production cost of bioactive compounds is quite high, due to the low contents in marine microalgae. Comprehensive utilization of marine microalgae for multiple compounds production instead of the sole product can be an efficient way to increase the economic feasibility of bioactive compounds production and improve the production efficiency. This paper discusses the metabolic network of marine microalgal compounds, and indicates their interaction in biosynthesis pathways. Furthermore, potential applications of co-production of multiple compounds under various cultivation conditions by shifting metabolic flux are discussed, and cultivation strategies based on environmental and/or nutrient conditions are proposed to improve the co-production. Moreover, biorefinery techniques for the integral use of microalgal biomass are summarized. These techniques include the co-extraction of multiple bioactive compounds from marine microalgae by conventional methods, super/subcritical fluids, and ionic liquids, as well as direct utilization and biochemical or thermochemical conversion of microalgal residues. Overall, this review sheds light on the potential of the comprehensive utilization of marine microalgae for improving bioeconomy in practical industrial application.

Drying Characteristics of Chlorella pyrenoidosa Using Oven and its Evaluation for Bio-Ethanol Production

The objective of this research is to study the influence of temperature on drying and changes in carbohydrate composition during the drying. Chlorella pyrenoidosa was dried in oven at various temperatures and initial weight 2 g. The initial moisture content of Chlorella pyrenoidosa was 487.2% dry weight and the composition was hemicellulose (62.76), cellulose (2.39), and lignin (0.46% dry weight). Every 5 min, the moisture content was recorded. The critical moisture contents of Chlorella pyrenoidosa at 50, 60, and 70 °C are 7.2, 3.9, and 3.1% dry weight, respectively. Meanwhile, the equilibrium water contents are 0.53, 0.32, and 0.12% dry weight, respectively. The carbohydrate content in Chlorella pyrenoidosa cell as a result FTIR analysis indicates that the higher temperature of drying the carbohydrate content increases. Drying of Chlorella pyrenoidosa at temperatures of 50, 60, and 70 °C will decrease moisture content without disturb carbohydrate molecule, so the carbohydrate content increases. Therefore, drying of Chlorella pyrenoidosa before converting become bio-ethanol will give benefit to increase the carbohydrate content and initial rupturing of it’s cell.

Production of algal biomass for its biochemical profile using slaughterhouse wastewater for treatment under axenic conditions

Slaughterhouse produce large amount of wastewater, containing high pollutant load in terms of protein, fats and meat pieces, might lead to source of non-point contamination. Various concentrations (25%, 50%, 75%, and 100%) of slaughterhouse wastewater were used to increase the algal biomass production, pollutants removal and biochemical profile analysis under controlled conditions of C. pyrenoidosa. Results showed that the maximum biomass yield 430 mg L-1 was achieved at 50% concentration of wastewater to other concentration of wastewater. Direct relation was observed in between pollution load and nutrient load of SHWW with biochemical profile of C. pyrenoidosa. The COD/BOD ratio (1.9) was found to be significant on the scale of degradability by algal biomass. Sufficient nutrient removal efficiencies (23-42%, 18-48%) and pollutant load efficiencies (17-31%, 7-29%) were observed. Findings showed that slaughterhouse wastewater is rich in nutrients, which can be utilized for algal biomass production and wastewater remediation for future endeavors.

Optimization of algae mixotrophic culture for nutrients recycling and biomass/lipids production in anaerobically digested waste sludge by various organic acids addition

Anaerobically digested waste sludge contains very high concentrations of ammonium and phosphate that are difficult to be purified using traditional processes. Mixotrophic culture of microalgae is a potential way to achieve ammonium and phosphate removal, while harvesting considerable biomass for biodiesel production. In this study, four typical volatile organic acids that could be potentially produced from sludge fermentation were tested for algal mixotrophic culture in anaerobically digested waste sludge. The results showed that the addition of propionate and isovaleric acid had no significant improvement on biomass production, and even inhibited algal growth at low concentration. Fortunately, the addition of acetic and n-butyric acid (initial C/N = 10) increased biomass production by1.9-2.4 times compared to the blank culture. Higher biomass production increased ammonium and orthophosphate removal to 88.3-97.1% and 80.4-93.0%, respectively. Moreover, the optimal addition of volatile organic acids enhanced lipids production by 3.9-6.3 times, while achieving higher saturation degree in biodiesels. The results suggest that adding these optimal volatile organic acids is suitable to enhance nutrients recycling and algal biodiesel production from anaerobically digested waste sludge.

Efficient harvesting of Chlorella pyrenoidosa and Scenedesmus obliquus cultivated in urban sewage by magnetic flocculation using nano-Fe3O4 coated with polyethyleneimine

In this work, a novel flocculation process by using nano-Fe₃O₄ coated with polyethyleneimine (Fe₃O₄@PEI) as magnetic seeds was developed to harvest the microalgae cultivated in urban sewage. Experiment results indicated that the harvest efficiency of Chlorella pyrenoidosa (0.5 g/L) was 98.92 ± 0.41% under the optimal conditions of Fe₃O₄@PEI dose of 20 mL/L, flocculation time of 20 min, and stirring speed of 800 rpm (3 min), while that of Scenedesmus obliquus (0.4 g/L) was 98.45 ± 0.35% under a Fe₃O₄@PEI dose of 16 mL/L, flocculation time of 15 min, and stirring speed of 730 rpm (3 min). Moreover, the process did not reduce the lipid content of microalgae and quality of biodiesel. After microalgae harvest, Fe₃O₄@PEI could be recovered by ultrasonication, re-wrapped with polyethyleneimine and reused to reduce operational cost.