Cyanobacterial biological nitrogen fixation as a sustainable nitrogen fertilizer for the production of microalgal oil

Comparative dataset on productivity, proximate, biochemical and pigment content of marine Gonyostomum sp. and freshwater Tetraedron sp. microalgae

The dataset includes a comparative analysis of Gonyostomum sp. and Tetraedron sp. to characterize their productivity, proximate composition, biochemical composition and pigments. Growth data were collected through cell density and optical density and subsequently mass-cultured to utilize biomass for other analyses. The onset of the stationary phase (12 to 18 days) varied between the species. Volumetric productivity, areal productivity, and SGR were also significantly higher (p ˂ 0.05) in Gonyostomum sp. whereas, Tetraedron sp. showed significantly higher (p ˂ 0.05) cell duplication time and cell doublings per day (K). Gonyostomum sp. showed significantly higher (p ˂ 0.05) protein (42.86±1.13%), carbohydrate (13.56±0.48%) and lipid (27.4 ± 0.69%) content than Tetraedron sp. Significantly higher (p ˂ 0.05) polyunsaturated fatty acids (PUFA) were obtained from both Gonyostomum sp. and Tetraedron sp. Non-essential amino acids were prevalent in both microalgae than essential amino acids. Significantly higher (p ˂ 0.05) chlorophyll-a (5.51±0.00), chlorophyll-b (2.27±0.04) and phycobiliprotein (2.32±0.05) were found in Tetraedron sp. Conversely, Gonyostomum sp. exhibited higher (p ˂ 0.05) carotenoid content (2.48±0.05). These findings may contribute to the screening and utilization of these microalgae in the aquaculture, pharmaceuticals, and nutraceuticals sectors.

Cyanobacterial elicitor enhances the biomass of Mentha piperita L. and improves the production of high-value rosmarinic acid under in vitro culture of apical meristem

BACKGROUND

Rosmarinic acid (RA), like other phenolic compounds, is sources of antioxidants and anti-inflammatory agents in medicinal plants. In vitro culture of plants can improve the medicinal plants' metabolite profile and phenolic compound quantity. To date, various methods have been proposed to increase this medicinal metabolite in plants, among which the use of bioelicitors can be mentioned. In the present study, a native isolate of heterocystous cyanobacteria, Nostoc spongiaeforme var. tenue ISB65, was used to stimulate the production of biomass and content of RA in Mentha piperita L. (peppermint) grown in vitro from apical meristem. Mentha piperita L. explants were inoculated in half strength Murashige and Skoog (1/2 MS) medium containing cyanobacterial lysate (CL). After 50 days of culturing, the growth indices, the content of photosynthetic pigments, and RA in control and treated plants were measured.

RESULTS

CL inoculation resulted in a significant enhancement in the vegetative growth indices of peppermint, including root and shoot length, plant biomass and leaf number. The content of photosynthetic pigments also increased in cyanobacteria-treated plants. Inoculation with CL increased the RA content by 2.3-fold, meaning that the plants treated with CL had the highest RA content (7.68 mg. g- 1 dry weight) compared to the control (3.42 mg. g- 1 dry weight). Additionally, HPLC analysis revealed the presence of several auxins in CL.

CONCLUSIONS

The presence of auxins and the chemical content of CL such as K+ and Ca2+, as regulators of metabolic pathways and molecular activities of cells, may be responsible for the enhanced growth and phenolic compounds of plants under tissue culture conditions. An improvement in RA content in the tissue culture of medicinal plants treated with CL was reported for the first time in this investigation.

Towards a sustainable transformation of municipal wastewater treatment plants into biofactories using advanced NH3-N recovery technologies: A review

Ammonia (NH3), as a prevalent pollutant in municipal wastewater discharges, can impair aquatic life and have a negatively impact on the environment. Proper wastewater treatment and management practices are essential to protect ecosystems and keep human populations healthy. Therefore, using highly effective NH3-N recovery technologies at wastewater treatment plants (WWTPs) is widely acknowledged as a necessity. In order to improve the overall efficiency of NH3 removal/recovery processes, innovative technologies have been generally applied to reduce its concentration when discharged into natural water bodies. This study reviews the current status of the main issues affecting NH3 recovery from municipal/domestic wastewater discharges. The current study investigated the ability to recover valuable resources, e.g., nutrients, regenerated water, and energy in the form of biogas through advanced and innovative methods in tertiary treatment to achieve higher efficiency towards sustainable wastewater and resource recovery facilities (W&RRFs). In addition, the concept of paradigm shifts from WWTP to a large/full scale W&RRF has been studied with several examples of conversion to innovative bio-factories producing materials. On the other hand, the carbon footprint and the high-energy consumption of the WWTPs were also considered to assess the sustainability of these facilities.

Microalgal upgrading of the fermentative biohydrogen produced from Bacillus coagulans via non-pretreated plant biomass

BACKGROUND

Hydrogen is a promising source of alternative energy. Fermentative production is more feasible because of its high hydrogen generation rate, simple operating conditions, and utilization of various organic wastes as substrates. The most significant constraint for biohydrogen production is supplying it at a low cost with fewer impurities.

RESULTS

Leaf biomass of Calotropis procera was used as a feedstock for a dark fermentative production of hydrogen by Bacillus coagulans AH1 (MN923076). The optimum operation conditions for biohydrogen production were 5.0% substrate concentrationand pH 9.0, at 35 °C. In which the biohydrogen yield was 3.231 mmol H2/g dry biomass without any pretreatments of the biomass. A freshwater microalga Oscillatroia sp was used for upgrading of the produced biohydrogen. It sequestrated 97 and 99% % of CO2 from the gas mixture when it was cultivated in BG11 and BG11-N media, respectively After upgrading process, the residual microalgal cells exhibited 0.21mg/mL of biomass yield,high content of chlorophyll-a (4.8 µg/mL) and carotenoid (11.1 µg/mL). In addition to Oscillatroia sp residual biomass showed a lipid yield (7.5-8.7%) on the tested media.

CONCLUSION

Bacillus coagulans AH1 is a promising tool for biohydrogen production avoiding the drawbacks of biomass pretreatment. Oscillatroia sp is encouraged as a potent tool for upgrading and purification of biohydrogen. These findings led to the development of a multiproduct biorefinery with zero waste that is more economically sustainable.

An integrated approach for the phycoremediation of Pb(II) and the production of biofertilizer using nitrogen-fixing cyanobacteria

In recent years, growing attention has been directed toward the phycoremediation of heavy metals from bodies of water; however, many challenges remain. The nitrogen requirements for algal growth in nutrient-poor waters can lead to substantial costs. Moreover, proper management of the metal-loaded biomass is a concern. This study assessed the performance of two nitrogen-fixing cyanobacteria, Anabaena sp. and Nostoc muscorum, in treating Pb(II)-contaminated water without nitrogen under batch and fed-batch modes, as well as the subsequent utilization of the produced biomass as a biofertilizer. After 12 days of the batch mode with initial Pb(II) concentrations of 10, 20, 35, and 60 mg/L, Pb(II) removal efficiencies were 98.90%, 98.95%, 97.20%, and 84.98% by Anabaena sp. and 88.00%, 73.10%, 54.54%, and 26.83% by N. muscorum, respectively. Anabaena sp. sustained growth and Pb(II) removal under the fed-batch mode by adjusting hydraulic retention time based on the influent Pb(II) concentration. Decontamination of the metal-loaded Anabaena sp. biomass was performed and resulted in a Pb(II) desorption of 93%. The desorbed Anabaena sp. extract provided the nutrient requirements for Chlorella vulgaris. The proposed strategy provides simultaneous Pb(II) bioremediation and biofertilizer production in a system driven by light energy, atmospheric N₂, and CO₂.

Fixing N2 into cyanophycin: continuous cultivation of Nostoc sp. PCC 7120

Abstract

Two diazotrophic cyanobacteria (Anabaena cylindrica PCC 7122 and Nostoc sp. PCC 7120) were cultivated to produce cyanophycin, a nitrogen reserve compound, under nitrogen fixing conditions. In preliminary continuous experiments, Nostoc sp. was shown to be more efficient, accumulating a higher amount of cyanophycin and showing a greater capability to fix atmospheric nitrogen in the biomass (67 mgN d−1 of fixed nitrogen per liter of culture). The operating conditions were then optimized to maximize the cyanophycin productivity: the effect of incident light intensity, residence time and nitrogen availability were investigated. Nitrogen availability and/or pH played a major role with respect to biomass production, whereas phosphorus limitation was the main variable to maximize cyanophycin accumulation. In this way, it was possible to achieve a stable and continuous production of cyanophycin (CGP) under diazotrophic conditions, obtaining a maximum cyanophycin productivity of 15 mgCGP L−1 d−1.

Key points

• Diazotrophic cyanobacteria produce stable amount of cyanophycin in continuous PBR.

• Nostoc sp. proved to be more efficient in producing cyanophycin than Anabaena sp.

• P deprivation is the major variable to increase cyanophycin productivity in continuous.

Screening and characterization of polyhydroxyalkanoate granules, and phylogenetic analysis of polyhydroxyalkanoate synthase gene PhaC in cyanobacteria

Using Nile Red and BODIPY 493/503 dye-staining and fluorescence microscopy, twenty cyanobacterial strains, including ten commercially available strains and ten environmental isolates from estuaries, freshwater ponds, and lagoons, were screened for the accumulation of ecologically important and potentially biotechnologically significant carbon storage granules such as polyhydroxyalkanoates (PHA). Dye-staining granules were observed in six strains. Three Synechocystis, spp. strains WHSYN, LSNM, and CGF-1, and a Phormidium-like sp. CGFILA were isolated from environmental sources and found to produce granules of polyhydroxyalkanoate (PHA) according to PHA synthase gene (phaC) PCR screening and ¹ H NMR analyses. The environmental isolate, Nodularia sp. Las Olas and commercially available Phormidium cf. iriguum CCALA 759 displayed granules but screened negative for PHA according to phaC PCR and ¹ H NMR analyses. Partial polyhydroxyalkanoate synthase subunit C (phaC) and 16S rRNA gene sequences obtained from the PHA-accumulating strains and analyzed alongside publicly available phaC, phaE, 16S rRNA, and 23S rRNA data help in understanding the distribution and evolutionary history of PHA biosynthesis within the phylum Cyanobacteria. The data show that the presence of phaC is highly conserved within the genus Synechocystis, and present in at least one isolate of Phormidium. Maximum likelihood analyses and cophylogenetic modeling of PHA synthase gene sequences provide evidence of a recent horizontal gene transfer event between distant genera of cyanobacteria related to Pleurocapsa sp. PCC 7327 and Phormidium-like sp. CGFILA. These findings will help guide additional screening for PHA producers, and may explain why some Phormidium species produce PHAs, while others do not.

Enhancement of Biomass and Lipid Productivities of Scenedesmus sp. Cultivated in the Wastewater of the Dairy Industry

Microalgae are photoautotrophic microorganisms capable of producing compounds with potential bioenergetic applications as an alternative energy source due to the imminent exhaustion of fossil fuels, their impact on the environment, and the constant population increase. The mass cultivation of these microorganisms requires high concentrations of nutrients, which is not profitable if analytical grade culture media are used. A viable alternative is the use of agro-industrial wastewater, due to the metabolic flexibility of these microorganisms and their ability to take advantage of the nutrients present in these substrates. For the reasons mentioned above, the effect of the cultivation in wastewater from cheese processing on the growth parameters and biomass composition of Scenedesmus sp. was evaluated, and its nutrient removal capacity determined. A high lipid concentration was obtained in the cultures with the dairy effluent (507.81 ± 19.09 mg g−1) compared to the standard culture medium, while the growth parameters remained similar to the control medium. Scenedesmus sp. achieved high percentages of nutrient assimilation of the wastewater used (88.41% and 97.07% for nitrogen and phosphorus, respectively). With the results obtained, the feasibility of cultivating microalgae in agro-industrial wastewater as an alternative culture medium that induces the accumulation of compounds with potential bioenergetic applications was verified.

Cyanobacteria as an eco-friendly resource for biofuel production: A critical review

Cyanobacteria are photosynthetic microorganisms which can be found in various environmental habitats. These photosynthetic bacteria are considered as promising feedstock for the production of the third- and the fourth-generation biofuels. The main subject of this review is highlighting the significant aspects of the biofuel production from cyanobacteria. The most recent investigations about the extraction or separation of the bio-oil from cyanobacteria are also adduced in the present review. Moreover, the genetic engineering of cyanobacteria for improving biofuel production and the impact of bioinformatics studies on the designing better-engineered strains are mentioned. The large-scale biofuel production is challenging, so the economic considerations to provide inexpensive biofuels are also cited. It seems that the future of biofuels is strongly dependent to the following items; understanding the metabolic pathways of the cyanobacterial species, progression in the construction of the engineered cyanobacteria, and inexpensive large-scale cultivation of them.

A review on anaerobic membrane bioreactors (AnMBRs) focused on modelling and control aspects

The use of anaerobic membrane bioreactor technology (AnMBR) is rapidly expanding. However, depending on the application, AnMBR design and operation is not fully mature, and needs further research to optimize process efficiency and enhance applicability. This paper reviews state-of-the-art of AnMBR focusing on modelling and control aspects. Quantitative environmental and economic evaluation has demonstrated substantial advantages in application of AnMBR to domestic wastewater treatment, but detailed modelling is less mature. While anaerobic process modelling is generally mature, more work is needed on integrated models which include coupling between membrane performance (including fouling) and the biological process. This should include microbial factors, which are important to generation of specific foulants such as soluble and particulate inert organics. Mature and well-established control tools, including better feedback control strategies are also required for both the process, and for fouling control.

Prospects, recent advancements and challenges of different wastewater streams for microalgal cultivation

Microalgae are recognized as one of the most powerful biotechnology platforms for many value added products including biofuels, bioactive compounds, animal and aquaculture feed etc. However, large scale production of microalgal biomass poses challenges due to the requirements of large amounts of water and nutrients for cultivation. Using wastewater for microalgal cultivation has emerged as a potential cost effective strategy for large scale microalgal biomass production. This approach also offers an efficient means to remove nutrients and metals from wastewater making wastewater treatment sustainable and energy efficient. Therefore, much research has been conducted in the recent years on utilizing various wastewater streams for microalgae cultivation. This review identifies and discusses the opportunities and challenges of different wastewater streams for microalgal cultivation. Many alternative routes for microalgal cultivation have been proposed to tackle some of the challenges that occur during microalgal cultivation in wastewater such as nutrient deficiency, substrate inhibition, toxicity etc. Scope and challenges of microalgal biomass grown on wastewater for various applications are also discussed along with the biorefinery approach.