Effects of various organic carbon sources on the growth and biochemical composition of Chlorella pyrenoidosa

Microalgal production and nutrient recovery under mixotrophic mode using cheese whey permeate

Mixotrophic microalgal solutions are efficient nutrient recovery methods, with potential to prolong the cultivation seasons in temperate climates. To improve operation sustainability, the study used landfill leachate for nitrogen source and whey permeate for phosphorus and organic carbon. A non-axenic polyculture, dominated by green algae, was cultivated in mixotrophic mode on glucose or whey permeate compared to a photoautotrophic control in outdoor pilot-scaled raceway ponds during Nordic spring and autumn. The whey permeate treatment had the highest algal growth rate and productivity (0.48 d-1, 183.8 mg L-1 d-1), nutrient removal (total nitrogen: 21.71 mg L-1 d-1, total phosphorus: 3.05 mg L-1 d-1) and recovery rate (carbon: 85.19 mg L-1 d-1, nitrogen: 17.01 mg L-1 d-1, phosphorus: 2.58 mg L-1 d-1). When grown in whey permeate, algal cultures demonstrated consistent productivity and biochemical composition in high (spring) and low light conditions (autumn), suggesting the feasibility of year-round production in Nordic conditions.

Feasibility study on heterotrophic utilization of galactose by Chlorella sorokiniana and promotion of galactose utilization through mixed carbon sources culture

BACKGROUND

The development of alternative carbon sources is important for reducing the cost of heterotrophic microalgae cultivation. Among cheap feedstocks, galactose is one of the most abundant sugars and can be easily obtained from many natural biomasses. However, it is generally difficult to be utilized by microalgae. In addition, the mechanism of its low utilization efficiency in heterotrophic cultivation is still unknown.

RESULTS

Among seven tested carbon sources, only glucose and acetate could be efficiently utilized by C. sorokiniana in heterotrophic cultivation while there were no apparent signs of utilization of other carbohydrates, including galactose, in regular heterotrophic cultivation. However, galactose could be utilized in cultures with high inoculation sizes. This confirmed that C. sorokiniana has a complete pathway for transporting and assimilating galactose under dark conditions, but the rate of galactose utilization is quite low. In addition, the galactose utilization was greatly enhanced in mixotrophic cultures, which indicated that galactose utilization could be enhanced by additional pathways that can enhance cell growth. Based on above results, a mixed carbon source culture strategy was proposed to improve the utilization rate of galactose, and a significant synergistic effect on cell growth was achieved in cultures using a mixture of galactose and acetate.

CONCLUSIONS

This study indicated that the galactose metabolism pathway may not be inherently deficient in Chlorophyta. However, its utilization rate was too low to be detected in regular heterotrophic cultivation. Mixed carbon source culture strategy was confirmed effective to improve the utilization rate of galactose. This study contributes to a deeper understanding of the utilization ability of difficultly utilized substrates in the heterotrophic cultivation of microalgae, which is of great significance for reducing the cost of heterotrophic cultivation of microalgae.

A Study on the Effect of Various Media and the Supplementation of Organic Compounds on the Enhanced Production of Astaxanthin from Haematococcus lacustris (Girod-Chantrans) Rostafinski (Chlorophyta)

Natural astaxanthin is in high demand due to its multiple health benefits. The microalga Haematococcus lacustris has been used for the commercial production of astaxanthin. In this study, we investigated the effects of six different media with and without a nitrogen source and supplementation with nine organic compounds on the growth and astaxanthin accumulation of H. lacustris. The highest astaxanthin contents were observed in cultures of H. lacustris in Jaworski's medium (JM), with a level of 9.099 mg/L in JM with a nitrogen source supplemented with leucine (0.65 g/L) and of 20.484 mg/L in JM without a nitrogen source supplemented with sodium glutamate (0.325 g/L). Six of the nine organic compounds examined (leucine, lysine, alanine, sodium glutamate, glutamine, and cellulose) enhanced the production of astaxanthin in H. lacustris, while malic acid, benzoic acid, and maltose showed no beneficial effects.

Algae as an alternative source of protein in poultry diets for sustainable production and disease resistance: present status and future considerations

Integrating algae into poultry diets offers a promising avenue for enhancing nutrition, boosting sustainability efforts, and potentially stimulating disease resistance. This comprehensive review delves into the essence, diversity, chemical composition, and nutritional merits of algae, spotlighting their emergence as innovative nutrient sources and health supplements for poultry. The growing interest in algae within poultry nutrition stems from their diverse nutritional profile, boasting a rich array of proteins, lipids, amino acids, vitamins, minerals, and antioxidants, thus positioning them as valuable feed constituents. A key highlight of incorporating both macroalgae and microalgae lies in their elevated protein content, with microalgae varieties like Spirulina and Chlorella exhibiting protein levels of up to 50-70%, outperforming traditional sources like soybean meal. This premium protein source not only furnishes vital amino acids crucial for muscular development and overall health in poultry but also serves as an exceptional reservoir of omega-3 fatty acids, notably eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), presenting multiple health benefits for both poultry and consumers alike. Moreover, algae boast antioxidant properties attributed to bioactive compounds like phycocyanin and astaxanthin, mitigating oxidative stress and boosting the bird's immune response, thereby fostering robust health and disease resilience. Incorporating macroalgae and microalgae into poultry diets yields positive impacts on performance metrics. Research evidence underscores the enhancement of growth rates, feed conversion ratios, carcass quality, and meat attributes in broilers, while in layers, supplementation promotes increased egg production, superior egg quality, and increased concentrations of beneficial nutrients such as omega-3 fatty acids. Furthermore, algae hold promise for mitigating the environmental footprint of poultry production, though significant outcomes from trials remain sporadic, necessitating further research to elucidate optimal dosages and blends for different algae species in poultry diets. Standardizing the composition of algae utilized in research is imperative, paving the way for potential applications in poultry nutrition as growth stimulants and substitutes for antibiotics. Nonetheless, a deeper understanding of dosage, combination, and mechanism of action through rigorous scientific investigation is key to unlocking algae's full potential within poultry nutrition.

Comparison of Different Pretreatment Processes Envisaging the Potential Use of Food Waste as Microalgae Substrate

A significant fraction of the food produced worldwide is currently lost or wasted throughout the supply chain, squandering natural and economic resources. Food waste valorization will be an important necessity in the coming years. This work investigates the ability of food waste to serve as a viable nutritional substrate for the heterotrophic growth of Chlorella vulgaris. The impact of different pretreatments on the elemental composition and microbial contamination of seven retail food waste mixtures was evaluated. Among the pretreatment methods applied to the food waste formulations, autoclaving was able to eliminate all microbial contamination and increase the availability of reducing sugars by 30%. Ohmic heating was also able to eliminate most of the contaminations in the food wastes in shorter time periods than autoclave. However, it has reduced the availability of reducing sugars, making it less preferable for microalgae heterotrophic cultivation. The direct utilization of food waste containing essential nutrients from fruits, vegetables, dairy and bakery products, and meat on the heterotrophic growth of microalgae allowed a biomass concentration of 2.2 × 108 cells·mL-1, being the culture able to consume more than 42% of the reducing sugars present in the substrate, thus demonstrating the economic and environmental potential of these wastes.

Valorization of environmental-burden waste towards microalgal metabolites production

The present study develops a novel concept of using waste media as an algal nutrient resource compared to the usual growth media with the aid of growth kinetics study and metabolite production abilities. Food- and agri-compost wastes are compact structures with elemental compounds for microbial media. As a part of the study, environ-burden wastes (3:1) as a food source for photosynthetic algae as a substitute for the costly nutrient media were proposed. The environment-burden waste was also envisaged for macromolecule production, i.e., 99200 μg/ml lipid, 112.5 μg/ml protein, and 8.75 μg/ml carbohydrate with different dilutions of agri-waste, bold basal media (BBM), and Food waste, respectively. The fabricated growth kinetics and dynamics showcased the unstructured models of different photosynthetic algal growth phases and the depiction of productivity and kinetic parameters. The theoretical maximum biomass concentration (Xp) was found to be more (0.871) with diluted agricompost media than the usual BBM (0.697). The X_Lim values were found to be 0.362, 0.323 and 0.209 for BBM, diluted agri-compost media and diluted food waste media, respectively. Overall, the study proposes a cleaner approach of utilizing the wastes as growth media through a circular economy approach which eventually reduces the growth media cost with integrated macromolecule production capabilities.

Effect of acute vs chronic stress on Polyhydroxybutyrate production by indigenous cyanobacterium

Fossil-based plastic has become a global-threat due to its high stability and transformation into more lethal forms such as micro plastics with time. An alternative should be found to combat this global enemy. Polyhydroxybutyrate or PHB can be such an alternative to plastic. Present study explores the synthesis of PHB in Neowollea manoromense, using two different cultivation-approaches: acute and chronic stress. This study has used 6 carbon sources and 3 different level of phosphate to study the accumulation of PHB along with lipid, carbohydrate, and proteins. Highest PHB in chronic-stress was achieved under glucose supplementation without phosphate at 21st day (156.5 ± 22.5 μg/mg), whereas in acute-stress, it was achieved under acetate without phosphate (91.0 ± 2.7 μg/mg). Despite higher accumulation in chronic-stress, high PHB productivity was achieved in acute-stress. Principal Component Analysis suggests that all the variables were positively correlated with each other. Here we first report PHB accumulation in Neowollea manoromense. This study highlights that acute-stress can be a powerful tool in establishment of a sustainable cyanobacteria based bio refinery for PHB production.

Chlorella sp.-ameliorated undesirable microenvironment promotes diabetic wound healing

Chronic diabetic wound remains a critical challenge suffering from the complicated negative microenvironments, such as high-glucose, excessive reactive oxygen species (ROS), hypoxia and malnutrition. Unfortunately, few strategies have been developed to ameliorate the multiple microenvironments simultaneously. In this study, Chlorella sp. (Chlorella) hydrogels were prepared against diabetic wounds. In vitro experiments demonstrated that living Chlorella could produce dissolved oxygen by photosynthesis, actively consume glucose and deplete ROS with the inherent antioxidants, during the daytime. At night, Chlorella was inactivated in situ by chlorine dioxide with human-body harmless concentration to utilize its abundant contents. It was verified in vitro that the inactivated-Chlorella could supply nutrition, relieve inflammation and terminate the oxygen-consumption of Chlorella-respiration. The advantages of living Chlorella and its contents were integrated ingeniously. The abovementioned functions were proven to accelerate cell proliferation, migration and angiogenesis in vitro. Then, streptozotocin-induced diabetic mice were employed for further validation. The in vivo outcomes confirmed that Chlorella could ameliorate the undesirable microenvironments, including hypoxia, high-glucose, excessive-ROS and chronic inflammation, thereby synergistically promoting tissue regeneration. Given the results above, Chlorella is considered as a tailor-made therapeutic strategy for diabetic wound healing.

Biotechnological Approaches for Biomass and Lipid Production Using Microalgae Chlorella and Its Future Perspectives

Heavy reliance on fossil fuels has been associated with increased climate disasters. As an alternative, microalgae have been proposed as an effective agent for biomass production. Several advantages of microalgae include faster growth, usage of non-arable land, recovery of nutrients from wastewater, efficient CO₂ capture, and high amount of biomolecules that are valuable for humans. Microalgae Chlorella spp. are a large group of eukaryotic, photosynthetic, unicellular microorganisms with high adaptability to environmental variations. Over the past decades, Chlorella has been used for the large-scale production of biomass. In addition, Chlorella has been actively used in various food industries for improving human health because of its antioxidant, antidiabetic, and immunomodulatory functions. However, the major restrictions in microalgal biofuel technology are the cost-consuming cultivation, processing, and lipid extraction processes. Therefore, various trials have been performed to enhance the biomass productivity and the lipid contents of Chlorella cells. This study provides a comprehensive review of lipid enhancement strategies mainly published in the last five years and aimed at regulating carbon sources, nutrients, stresses, and expression of exogenous genes to improve biomass production and lipid synthesis.

Mechanisms and application of microalgae on removing emerging contaminants from wastewater: A review

This study reviews the development of the ability of microalgae to remove emerging contaminants (ECs) from wastewater. Contaminant removal by microalgae-based systems (MBSs) includes biosorption, bioaccumulation, biodegradation, photolysis, hydrolysis, and volatilization. Usually, the existence of ECs can inhibit microalgae growth and reduce their removal ability. Therefore, three methods (acclimation, co-metabolism, and algal-bacterial consortia) are proposed in this paper to improve the removal performance of ECs by microalgae. Finally, due to the high removal performance of contaminants from wastewater by algal-bacterial consortia systems, three kinds of algal-bacterial consortia applications (algal-bacterial activatedsludge, algal-bacterial biofilm reactor, and algal-bacterial constructed wetland system) are recommended in this paper. These applications are promising for ECs removal. But most of them are still in their infancy, and limited research has been conducted on operational mechanisms and removal processes. Extra research is needed to clarify the applicability and cost-effectiveness of hybrid processes.

Enhancement of Carbon Conversion and Value-Added Compound Production in Heterotrophic Chlorella vulgaris Using Sweet Sorghum Extract

High-cost carbon sources are not economical or sustainable for the heterotrophic culture of Chlorella vulgaris. In order to reduce the cost, this study used sweet sorghum extract (SE) and its enzymatic hydrolysate (HSE) as alternative carbon sources for the heterotrophic culture of Chlorella vulgaris. Under the premise of the same total carbon concentration, the value-added product production performance of Chlorella vulgaris cultured in HSE (supplemented with nitrogen sources and minerals) was much better than that in the glucose medium. The conversion rate of the total organic carbon and the utilization rate of the total nitrogen were both improved in the HSE system. The biomass production and productivity using HSE reached 2.51 g/L and 0.42 g/L/d, respectively. The production of proteins and lipids using HSE reached 1.17 and 0.35 g/L, respectively, and the production of chlorophyll-a, carotenoid, and lutein using HSE reached 30.42, 10.99, and 0.88 mg/L, respectively. The medium cost using HSE decreased by 69.61% compared to glucose. This study proves the feasibility and practicability of using HSE as a carbon source for the low-cost heterotrophic culture of Chlorella vulgaris.

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.

Synergistic effect of growth conditions and organic carbon sources for improving biomass production and biodiesel quality by the microalga Choricystis minor var. minor

In the search for microalgae species with potential for biodiesel production, Choricystis minor var. minor has been seen as a promising source of biomass due to its high lipid content and the satisfactory characteristics of its fatty acid methyl esters (FAMEs). For this reason, the objective of this study was to investigate the synergistic effect of growth conditions and organic carbon sources on cultivation of this microalga. To do so, experimental cultivations were conducted in photoautotrophic, heterotrophic and mixotrophic metabolisms using glucose, fructose, glycerol or sucrose - in growth conditions that use organic carbon. Thus, growth parameters of the cultures were evaluated and at the end of the cultivations, FAMEs yield and profile were determined by gas chromatography, the efficiency of carbon conversion into biomass was evaluated and a microbial analysis was conducted. Regarding growth conditions, the findings have confirmed that, regardless of the organic carbon source used, the heterotrophic and mixotrophic metabolisms can present advantages over the photoautotrophic one. In addition, biomass production was higher with the use of glucose than with other organic carbon sources, regardless of growth condition (heterotrophic or mixotrophic). Moreover, cultivations with the addition of CO₂ have converted carbon into biomass less efficiently. On the other hand, photoautotrophic cultures presented the lowest bacterial load. In comparison to photoautotrophic and mixotrophic, heterotrophic cultures have led to lower FAMEs content and higher yields of unsaturated fatty acids. The most satisfactory FAMEs profile for biodiesel production was obtained with mixotrophic growth using fructose.

Bioremediation of Pyropia-processing wastewater coupled with lipid production using Chlorella sp

Pyropia-processing wastewater (PPW) contains diverse organic nutrients and causes environmental pollution. To explore the nutrient removal efficiency and growth performance of Chlorella sp. on PPW, the cultures were conducted in different culture substrates. Results showed that, after 7 days of incubation, the removal rates of total nitrogen (TN), total phosphorus (TP) and phycobiliprotein (PP) all reached more than 90% by cultivating Chlorella sp. C2 and C. sorokiniana F-275 in PPW. The chemical oxygen demand (COD) removal efficiencies could be over 50%. Meanwhile, the increments of biomass in two tested Chlorella strains were 1.39 and 4.89 times higher than those of BG11 and BBM substrates and the increases in lipid productivity were 1.34 and 10.18- fold, respectively. The C18:3 fatty acid proportions were markedly reduced by 27.89% and 29.10%. These results suggest that Chlorella sp. could efficiently reduce various nutrients in PPW and simultaneously accumulate higher biomass with higher biodiesel characteristics.

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.

Micropollutants cometabolism of microalgae for wastewater remediation: Effect of carbon sources to cometabolism and degradation products

This study investigated the impacts of selective sole carbon source-induced micropollutants (MPs) cometabolism of Chlorella sp. by: (i) extracellular polymeric substances (EPS), superoxide dismutase and peroxidase enzyme production; (ii) MPs removal efficiency and cometabolism rate; (iii) MPs' potential degradation products identification; and (iv) degradation pathways and validation using the Eawag database to differentiate the cometabolism of Chlorella sp. with other microbes. Adding the sole carbon sources in the presence of MPs increased EPS and enzyme concentrations from 2 to 100-fold in comparison with only sole carbon sources. This confirmed that MPs cometabolism had occurred. The removal efficiencies of tetracycline, sulfamethoxazole, and bisphenol A ranged from 16-99%, 32-92%, and 58-99%, respectively. By increasing EPS and enzyme activity, the MPs concentrations accumulated in microalgae cells also fell 400-fold. The cometabolism process resulted in several degradation products of MPs. This study drew an insightful understanding of cometabolism for MPs remediation in wastewater. Based on the results, proper carbon sources for microalgae can be selected for practical applications to remediate MPs in wastewater while simultaneously recovering biomass for several industries and gaining revenue.

Selective carbon sources and salinities enhance enzymes and extracellular polymeric substances extrusion of Chlorella sp. for potential co-metabolism

This study investigated the extracellular polymeric substance (EPS) and enzyme extrusion of Chlorella sp. using seven carbon sources and two salinities for potential pollutant co-metabolism. Results indicated that the levels of biomass, EPS and enzymes of microalgae cultured with glucose and saccharose outcompeted other carbon sources. For pigment production, glycine received the highest chlorophyll and carotene, up to 10 mg/L. The EPS reached 30 mg/L, having doubled the amount of protein than carbohydrate. For superoxide dismutase and peroxidase enzymes, the highest concentrations were beyond 60 U/ml and 6 nmol/d.ml, respectively. This amount could be potentially used for degrading 40% ciprofloxacin of concentration 2000 µg/L. When increasing salinity from 0.1% to 3.5%, the concentrations of pigment, EPS and enzymes rose 3 to 30 times. These results highlighted that certain carbon sources and salinities could induce Chlorella sp. to produce EPS and enzymes for pollutant co-metabolism and also for revenue-raising potential.

Evaluation of the Antibacterial Material Production in the Fermentation of Bacillus amyloliquefaciens-9 from Whitespotted Bamboo Shark (Chiloscyllium plagiosum)

Bacillus amyloliquefaciens-9 (GBacillus-9), which is isolated from the intestinal tract of the white-spotted bamboo shark (Chiloscyllium plagiosum), can secrete potential antibacterial materials, such as β-1,3-1,4-glucanase and some antimicrobial peptides. However, the low fermentation production has hindered the development of GBacillus-9 as biological additives. In this study, the Plackett–Burman design and response surface methodology were used to optimize the fermentation conditions in a shake flask to obtain a higher yield and antibacterial activity of GBacillus-9. On the basis of the data from medium screening, M9 medium was selected as the basic medium for fermentation. The data from the single-factor experiment showed that sucrose had the highest antibacterial activity among the 10 carbon sources. The Plackett–Burman design identified sucrose, NH₄Cl, and MgSO₄ as the major variables altering antibacterial activity. The optimal concentrations of these compounds to enhance antibacterial activity were assessed using the central composite design. Data showed that sucrose, NH₄Cl, and MgSO₄ had the highest antibacterial activities at concentrations of 64.8, 1.84, and 0.08 g L⁻¹, respectively. The data also showed that the optimal fermentation conditions for the antibacterial material production of GBacillus-9 were as follows: Inoculum volume of 5%, initial pH of 7.0, temperature of 36 °C, rotating speed of 180 rpm, and fermentation time of 10 h. The optimal fermentation medium and conditions achieved to improve the yield of antibacterial materials for GBacillus-9 can enhance the process of developing biological additives derived from GBacillus-9.

Lipids production and nutrients recycling by microalgae mixotrophic culture in anaerobic digestate of sludge using wasted organics as carbon source

Insufficient organics in anaerobic digestate of sludge limited algal mixotrophic culture and caused low lipids production. In this study, enhancing lipids production and pollutants removal by adding acidified starch wastewater was tested for Chlorella pyrenoidosa mixotrophic culture. The results showed that an optimal addition of acidified starch wastewater into anaerobic digestate of sludge (1:1, v/v) improved biomass and lipids production by 0.5-fold (to 2.59 g·L^-1) and 3.2-fold (87.3 mg·L^-1·d^-1), respectively. The acidified starch wastewater addition also improved the quality of algal biodiesel with higher saturation (typically in C16:0 and C18:0). In addition, 62% of total organic carbon, 99% of ammonium and 95% of orthophosphate in mixed wastewater were effectively removed by microalgae. This study provides a promising way to improve biodiesel production and nutrients recovery from anaerobic digestate of sludge using waste carbon source.

Comprehensive evaluation of a cost-effective method of culturing Chlorella pyrenoidosa with unsterilized piggery wastewater for biofuel production

BACKGROUND

The utilization of Chlorella for the dual goals of biofuel production and wastewater nutrient removal is highly attractive. Moreover, this technology combined with flue gas (rich in CO₂) cleaning is considered to be an effective way of improving biofuel production. However, the sterilization of wastewater is an energy-consuming step. This study aimed to comprehensively evaluate a cost-effective method of culturing Chlorella pyrenoidosa in unsterilized piggery wastewater for biofuel production by sparging air or simulated flue gas, including algal biomass production, lipid production, nutrient removal rate and the mutual effects between algae and other microbes.

RESULTS

The average biomass productivity of C. pyrenoidosa reached 0.11 g L^-1 day^-1/0.15 g L^-1 day^-1 and the average lipid productivity reached 19.3 mg L^-1 day^-1/30.0 mg L^-1 day^-1 when sparging air or simulated flue gas, respectively. This method achieved fairish nutrient removal efficiency with respect to chemical oxygen demand (43.9%/55.1% when sparging air and simulated flue gas, respectively), ammonia (98.7%/100% when sparging air and simulated flue gas, respectively), total nitrogen (38.6%/51.9% when sparging air or simulated flue gas, respectively) and total phosphorus (42.8%/60.5% when sparging air or simulated flue gas, respectively). Culturing C. pyrenoidosa strongly influenced the microbial community in piggery wastewater. In particular, culturing C. pyrenoidosa enriched the abundance of the obligate parasite Vampirovibrionales, which can result in the death of Chlorella.

CONCLUSION

The study provided a comprehensive evaluation of culturing C. pyrenoidosa in unsterilized piggery wastewater for biofuel production. The results indicated that this cost-effective method is feasible but has considerable room for improving. More importantly, this study elucidated the mutual effects between algae and other microbes. In particular, a detrimental effect of the obligate parasite Vampirovibrionales on algal biomass and lipid production was found.

Food waste compost as an organic nutrient source for the cultivation of Chlorella vulgaris

The present study investigates the prospective of substituting inorganic medium with organic food waste compost medium as a nutrient supplement for the cultivation of Chlorella vulgaris FSP-E. Various percentages of compost mixtures were replaced in the inorganic medium to compare the algal growth and biochemical composition. The use of 25% compost mixture combination was found to yield higher biomass concentration (11.1%) and better lipid (10.1%) and protein (2.0%) content compared with microalgae cultivation in fully inorganic medium. These results exhibited the potential of combining the inorganic medium with organic food waste compost medium as an effective way to reduce the cultivation cost of microalgae and to increase the biochemical content in the cultivated microalgae.

Tofu whey wastewater is a promising basal medium for microalgae culture

Tofu whey wastewater (TWW) is an abundant, nutrient riched and safety wastewater and is regarded as an excellent alternative medium in fermentation. In this study, the feasibility of algal cultivation using TWW as the basal medium was investigated. Results indicated that through simple pH adjustment, TWW presented a better culture performance at autotrophic, heterotrophic, and mixotrophic modes compared with that of regular green algae medium, BG-11. The biomass productivities of Chlorella pyrenoidosa at each trophic mode were 4.76, 1.97, and 2.08 times higher than that cultured in BG-11 medium, respectively. Although a comparative or even lower lipid and protein content was obtained, much higher lipid and protein productivities were obtained in TWW compared to that of BG-11. The algal biomass accumulated in TWW can be used to produce high-value products. Therefore, TWW is a better alternative medium for efficient algal culture.

Heterotrophic culture of Chlorella pyrenoidosa using sucrose as the sole carbon source by co-culture with immobilized yeast

Glucose is normally used as the carbon source for heterotrophic cultivation of algal cells, whereas sucrose is difficult to be heterotrophicly utilized by them. In this study, a new co-culture system was developed through mixed culture of Chlorella pyrenoidosa with immobilized Saccharomyces cerevisiae in the dark to effectively obtain pure algal suspension using sucrose as only carbon source. In this system, a pure algal suspension with a concentration of 2.08g/L was obtained. The lipid content reached 29%, which was higher than that obtained in glucose contained system. In addition, the immobilized yeast beads were repeatedly used for at least three times. Through immobilization, the choice for the yeast strains that are able to hydrolyze sucrose was not limited by its product and pure algal suspension was efficiently obtained. This strategy may effectively decrease the cost of carbon source in the heterotrophic cultivation of microalgae.

Kelp waste extracts combined with acetate enhances the biofuel characteristics of Chlorella sorokiniana

To probe the effect of kelp waste extracts (KWE) combined with acetate on biochemical composition of Chlorella sorokiniana, the cultures were performed under independent/combined treatment of KWE and acetate. The results showed that high cell density and biomass were obtained by KWE combined with acetate treatments, whose biomass productivity increased by 79.69-102.57% and 20.04-35.32% compared with 3.0gL-1 acetate and KWE treatments respectively. The maximal neutral lipid per cell and lipid productivity were gained in KWE combined with 3.0gL-1 acetate treatment, which increased by 16.32% and 129.03% compared with 3.0gL-1 acetate, and 253.35% and 70.74% compared with KWE treatment. Meanwhile, C18:3n3 and C18:2n6c contents were reduced to 4.90% and 11.88%, whereas C16:0 and C18:1n9c were improved to 28.71% and 37.76%. Hence, supplementing appropriate acetate in KWE cultures is supposed to be a great potential method for large-scale cultivation of C. sorokiniana to generate biofuel.

Heterotrophic cultivation of Chlorella pyrenoidosa using sucrose as the sole carbon source by co-culture with Rhodotorula glutinis

Heterotrophic cultivation of microalgae is a feasible alternative strategy to avoid the light limitation of photoautotrophic culture, but the heterotrophic utilization of disaccharides is difficult for microalgae. Aimed at this problem, a co-culture system was developed by mix culture of C. pyrenoidosa and R. glutinis using sucrose as the sole carbon source. In this system, C. pyrenoidosa could utilize glucose and fructose which were hydrolyzed from sucrose by R. glutinis. The highest specific growth rate and final cell number proportion of algae was 1.02day(-1) and 45%, respectively, when cultured at the initial algal cell number proportion of 95.24% and the final algal cell density was 111.48×10(6)cells/mL. In addition, the lipid content was also promoted due to the synergistic effects in mix culture. This study provides a novel approach using sucrose-riched wastes for the heterotrophic culture of microalgae and may effectively decrease the cost of carbon source.

Effect of nitrogen regime on microalgal lipid production during mixotrophic growth with glycerol

Mixotrophic growth of microalgae to boost lipid production is currently under active investigation. Such a process could be of practical importance if a cheap source of organic carbon, such as waste glycerol from biodiesel production, could be used. Several previous studies have already demonstrated that this carbon source can be used by different indigenous strains of microalgae. In this study it is shown that different nitrogen limitation strategies can be applied to further increase lipid production during growth with glycerol. In one strategy, cultures were grown in nitrogen replete medium and then resuspended in nitrogen free medium. In a second strategy, cultures were grown with different initial concentrations of nitrate. Lipid production by the two microalgal strains used, Chlorella sorokiniana (PCH02) and Chlorella vulgaris (PCH05), was shown to be boosted by strategies of nitrogen limitation, but they responded differently to how nitrogen limitation was imposed.

Evaluation of indigenous fresh water microalga Scenedesmus obtusus for feed and fuel applications: Effect of carbon dioxide, light and nutrient sources on growth and biochemical characteristics

Scenedesmus obtusus, a freshwater microalga, was evaluated for its growth and biochemical characteristics under various culture conditions. S. obtusus was tolerant at all tested CO2 concentrations up to 20%. Among the different nitrogen sources, urea showed enhanced biomass productivities up to 2-fold compared to control, where the nitrogen source was sodium nitrate. Light intensity and photoperiod had a significant effect on growth rate and biomass productivity. The growth rate was observed maximum under continuous light exposure at the light intensities, 30μmolm(-2)sec(-1) and 60μmolm(-2)sec(-1) The species was able to tolerate the salinity levels up to 25mM NaCl, where, the increase in the concentration of NaCl suppressed the growth. Ammonium acetate and glycine showed better growth rate and biomass productivity indicating mixotrophic ability of S. obtusus. Supplementation of acetate and bicarbonate significantly enhanced the biomass productivity. Biodiesel properties of S. obtusus cultivated at various culture conditions were estimated.

Measuring the Composition and Stable-Isotope Labeling of Algal Biomass Carbohydrates via Gas Chromatography/Mass Spectrometry

We have developed a method to measure carbohydrate composition and stable-isotope labeling in algal biomass using gas chromatography/mass spectrometry (GC/MS). The method consists of two-stage hydrochloric acid hydrolysis, followed by chemical derivatization of the released monomer sugars and quantification by GC/MS. Fully (13)C-labeled sugars are used as internal standards for composition analysis. This convenient, reliable, and accurate single-platform workflow offers advantages over existing methods and opens new opportunities to study carbohydrate metabolism of algae under autotrophic, mixotrophic, and heterotrophic conditions using metabolic flux analysis and isotopic tracers such as (2)H2O and (13)C-glucose.

Effect of kelp waste extracts on the growth and lipid accumulation of microalgae

Kelp waste extracts (KWE) contained massive soluble sugars, amino acids and various mineral elements. To probe the effects of KWE on microalgal physiological and biochemical responses, the cultures were carried out under the different dilutions. The results showed that 8.0% KWE increased the biomass productivities and total lipid contents of Chlorella strains dramatically, which were 1.83-31.86 times and 20.78-25.91% higher than that of the control. Phaeodactylum tricornutum and Spirulina maxima presented a better growth performance in 1.0% and 4.0% treatment respectively, while their lipid accumulation were not enhanced. In Chlorella-Arc, Chlorella sorokiniana and P. tricornutum, the contents of saturated and monounsaturated fatty acids could be increased, and polyunsaturated fatty acids could be decreased under the conditions of high concentration of KWE (6.0-8.0%). Briefly, KWE facilitated to enhance the biomass productivity and lipid content of Chlorella strains, also improved the fatty acid compositions for biodiesel production.

Multi-objective optimization of media nutrients for enhanced production of algae biomass and fatty acid biosynthesis from Chlorella pyrenoidosa NCIM 2738

This study aimed to optimize significant medium nutrient parameters for maximization of algal lipid and biomass production by using multi objective optimization strategy. Nutrients (nitrate, phosphate and carbohydrate) were investigated to improve the lipid accumulation, biomass production and carbohydrate consumption individually and cumulative manner using a central composite design for the Chlorella pyrenoidosa NCIM 2738 cultivation. Maximum lipid, algal biomass and carbohydrate utilization for individual response optimization were found 34.8% (w/w), 1464.3mgL(-1) and 93.4%, respectively at different optimum level of selected parameters. Whereas, maximum lipid accumulation, biomass production and glucose consumption values in multi-response optimization were observed 28.9%, 1271.2mgL(-1) and 89.2%, respectively at optimum level of 16.8mM NaNO3, 300.9μM K2HPO4 and 2.6% (w/v) glucose. The overall enhancements in lipid productivities by single and multi-response optimization in comparison with control medium conditions were found 2.35 and 2.90-fold with productivity level of 24.8 and 30.6mgL(-1)day(-1), respectively.

Effects of various amino acids as organic nitrogen sources on the growth and biochemical composition of Chlorella pyrenoidosa

This study investigated the effects of eighteen l-amino acids on the growth and biochemical composition of Chlorella pyrenoidosa. Under the nitrate deficiency condition, ten l-amino acids were found to exert stronger stimulative effects on the algal growth than the other amino acids. After 10-day culture, addition of 0.5gL(-1) the above mentioned ten amino acids significantly increased the cellular protein contents by 441.3-110.8%, respectively, and significantly decreased the carbohydrate contents by 60.7-16.2%, respectively. Under the normal nitrate condition, the cellular biochemical composition was not significantly affected by addition of serine, leucine, proline, aspartic acid, asparagine, and glycine, whereas addition of aspartic acid and arginine increased the algal biomass by 110.2% and 62.8% compared with the control. Finally, the significance of this work in the biotechnological application of culturing C. pyrenoidosa in organic wastewater rich in amino acids was further discussed.

Nutrients removal and lipids production by Chlorella pyrenoidosa cultivation using anaerobic digested starch wastewater and alcohol wastewater

The cultivation of microalgae Chlorella pyrenoidosa (C. pyrenoidosa) using anaerobic digested starch wastewater (ADSW) and alcohol wastewater (AW) was evaluated in this study. Different proportions of mixed wastewater (AW/ADSW=0.176:1, 0.053:1, 0.026:1, v/v) and pure ADSW, AW were used for C. pyrenoidosa cultivation. The different proportions between ADSW and AW significantly influenced biomass growth, lipids production and pollutants removal. The best performance was achieved using mixed wastewater (AW/ADSW=0.053:1, v/v), leading to a maximal total biomass of 3.01±0.15 g/L (dry weight), lipids productivity of 127.71±6.31 mg/L/d and pollutants removal of COD=75.78±3.76%, TN=91.64±4.58% and TP=90.74±4.62%.

Enhanced biofuel production potential with nutritional stress amelioration through optimization of carbon source and light intensity in Scenedesmus sp. CCNM 1077

Microalgal mixotrophic cultivation is one of the most potential ways to enhance biomass and biofuel production. In the present study, first of all ability of microalgae Scenedesmus sp. CCNM 1077 to utilize various carbon sources under mixotrophic growth condition was evaluated followed by optimization of glucose concentration and light intensity to obtain higher biomass, lipid and carbohydrate contents. Under optimized condition i.e. 4 g/L glucose and 150 μmol m(-2) s(-1) light intensity, Scenedesmus sp. CCNM 1077 produced 1.2g/L dry cell weight containing 23.62% total lipid and 42.68% carbohydrate. Addition of glucose shown nutritional stress ameliorating effects and around 70% carbohydrate and 25% total lipid content was found with only 21% reduction in dry cell weight under nitrogen starved condition. This study shows potential application of mixotrophically grown Scenedesmus sp. CCNM 1077 for bioethanol and biodiesel production feed stock.