Ultrasonic-assisted green extraction and incorporation of Spirulina platensis bioactive components into turmeric essential oil-in-water nanoemulsion for enhanced antioxidant and antimicrobial activities.

The utilization of essential oils as natural antioxidants and preservatives is limited by high volatility, poor water solubility, and long-term instability. To address this, a novel ultrasonic-assisted method was used to prepare and stabilize a nanoemulsion of turmeric essential oil-in-water, incorporating bioactive components extracted from Spirulina platensis. Ultrasonic treatment enhanced the extraction efficacy and nanoemulsion stability. Algal biomass subjected to ultrasonic treatment (30 min at 80% amplitude) yielded a dry extract of 73.66 ± 3.05%, with the highest protein, phenolic, phycocyanin, and allophycocyanin content, as well as maximum emulsifying activity. The resulting nanoemulsion (5% oil, 0.3% extract, 10 min ultrasonic treatment) showed reduced particle size (173.31 ± 2.24 nm), zeta potential (-36.33 ± 1.10 mV), low polydispersity index, and enhanced antioxidant and antibacterial properties. Rheology analysis indicated shear-thinning behavior, while microscopy and spectroscopy confirmed structural changes induced by ultrasonic treatment and extract concentration. This initiative developed a novel ultrasonic-assisted algal-based nanoemulsion with antioxidant and antibacterial properties.

Enhancing microalgal biomass production in lab-scale raceway ponds through innovative computational fluid dynamics-based electrode deflectors.

The design of novel electrode deflector structures (EDSs) introduced a promising strategy for enhancing raceway ponds performance, increasing carbon fixation, and improving microalgal biomass accumulation. The computational fluid dynamics, based flow field principles, proved that the potency of arc-shaped electrode deflector structures (A-EDS) and spiral electrode deflector structures (S-EDS) were optimal. These configurations yielded superior culture effects, notably reducing dead zones by 9.1% and 11.7%, while elevating biomass increments of 14.7% and 11.5% compared to the control, respectively. In comparison to scenarios without electrostatic field application, the A-EDS group demonstrated pronounced post-stimulation growth, exhibiting an additional biomass increase of 11.2%, coupled with a remarkable 23.6% surge in CO2 fixation rate and mixing time reduction by 14.7%. A-EDS and S-EDS, combined with strategic electric field integration, provided a theoretical basis for promoting microalgal biomass production and enhancing carbon fixation in a raceway pond environment to similar production practices.

Regulation of microclimate and shading effects of microalgal photobioreactors on rooftops: Microalgae as a promising emergent for green roof technology.

Urban areas remarkably affect global public health due to their emissions of greenhouse gases and poor air quality. Although urban areas only cover 2% of the Earth's surface, they are responsible for 80% of greenhouse gas emissions. Dense buildings limit vegetation, leading to increased air pollution and disruption of the local and regional carbon cycle. The substitution of urban gray roofs with microalgal green roofs has the potential to improve the carbon cycle by sequestering CO2 from the atmosphere. Microalgae can fix 15-50 times more CO2 than other types of vegetation. Advanced microalgal-based green roof technology may significantly accelerate the reduction of atmospheric CO2 in a more effective way. Microalgal green roofs also enhance air quality, oxygen production, acoustic isolation, sunlight absorption, and biomass production. This endeavor yields the advantage of simultaneously generating protein, lipids, vitamins, and a spectrum of valuable bioactive compounds, including astaxanthin, carotenoids, polysaccharides, and phycocyanin, thus contributing to a green economy. The primary focus of the current work is on analyzing the ecological advantages and CO2 bio-fixation efficiency attained through microalgal cultivation on urban rooftops. This study also briefly examines the idea of green roofs, clarifies the ecological benefits associated with them, discusses the practice of growing microalgae on rooftops, identifies the difficulties involved, and the positive aspects of this novel strategy.

Effective removing of rotifer contamination in microalgal lab-scale raceway ponds by light-induced phototaxis coupled with high-voltage pulse electroshock.

Rotifer reproduction control in open microalgae cultivation systems poses a significant challenge for large-scale industries. Conventional methods, such as electric, meshing, and chemical techniques, are often expensive, ineffective, and may have adverse environmental-health impacts. This study investigated a promising control technique through light-induced phototaxis to concentrate rotifers in a specific spot, where they were electroshocked by local-limited exposure dose. The results showed that the rotifers had the most pronounced positive and negative phototropism with phototaxis rates of 66.7 % and -78.8 %, respectively, at blue-light irradiation of 30 µmol∙m-2∙s-1 and red-light irradiation of 22.5 µmol∙m-2∙s-1 for 20 min. The most effective electroshock configuration employed 1200 V/cm for 15 min with a 1-second cycle time and a 10 % duty cycle, resulting in a 75.0 % rotifer removal rate without impacting microalgae growth. The combination of the two light beams could effectively lead rotifers to designated areas where they were electrocuted successfully.

Sunlight filtered via translucent-colored polyvinyl chloride sheets enhanced the light absorption capacity and growth of Arthrospira platensis cultivated in a pilot-scale raceway pond.

In this research, the effects of filtered sunlight traveling through translucent-colored polyvinyl chloride (PVC) sheets on the photoconversion efficiency of Arthrospira platensis are investigated. Filtered sunlight improves the phycobilisome's capacity to completely absorb and transport it to intracellular photosystems. Findings indicated that filtered sunlight via orange-colored PVC sheet increased biomass dry weight by 21% (2.80 g/L), while under blue-colored PVC sheet decreased by 32% (1.49 g/L), when compared with translucent-colored (control) PVC sheet (2.19 g/L) after 120 h of culture. The meteorological conditions during the 1st week of cultivation reported higher light flux than the subsequent weeks. Furthermore, sunlight filtered through orange PVC sheet enhanced protein, allophycocyanin, phycocyanin, chlorophyll-a and carotenoids synthesis by 13%, 15%, 13%, 22%, and 27%, respectively. This practical and inexpensive solar radiation filtration system supports large-scale production of tailored bioactive compounds from microalgae with high growth rate.

Advanced microbial protein technologies are promising for supporting global food-feed supply chains with positive environmental impacts.

This study focuses on microbial protein (MP) as a promising food-feed alternative source that may contribute to overcoming the increased food challenge. It analyzes the traditional and advanced MP technologies, their progress, sustainability, and environmental limitations. Traditional MP technologies are reliable for global food-feed supply chains but face higher production costs and negative environmental impacts. Advanced MP systems utilize sustainable sources like food waste, but limited availability and characteristics necessitate pretreatments. Power-to-protein technology looks promising due to its ability to capture CO2 and avoiding external organic carbon addition, although more research is still needed. Cultivating indigenous microorganisms in agricultural wastewater, such as biofloc technology, offer potential for nutrient recovery and reduced environmental impacts. Microalgal biomass is sustainable but faces challenges of low palatability, productivity, and high costs, while ongoing studies try to solve these challenges. This review concludes that the advanced MP technologies are environmentally friendly and promising, while further studies are necessary to enhance performance and commercial implementation.

Molecular approaches to enhance astaxanthin biosynthesis; future outlook: engineering of transcription factors in Haematococcus pluvialis.

Microalgae are the preferred species for producing astaxanthin because they pose a low toxicity risk than chemical synthesis. Astaxanthin has multiple health benefits and is being used in: medicines, nutraceuticals, cosmetics, and functional foods. Haematococcus pluvialis is a model microalga for astaxanthin biosynthesis; however, its natural astaxanthin content is low. Therefore, it is necessary to develop methods to improve the biosynthesis of astaxanthin to meet industrial demands, making its commercialization cost-effective. Several strategies related to cultivation conditions are employed to enhance the biosynthesis of astaxanthin in H. pluvialis. However, the mechanism of its regulation by transcription factors is unknown. For the first time, this study critically reviewed the studies on identifying transcription factors, progress in H. pluvialis genetic transformation, and use of phytohormones that increase the gene expression related to astaxanthin biosynthesis. In addition, we propose future approaches, including (i) Cloning and characterization of transcription factors, (ii) Transcriptional engineering through overexpression of positive regulators or downregulation/silencing of negative regulators, (iii) Gene editing for enrichment or deletion of transcription factors binding sites, (iv) Hormonal modulation of transcription factors. This review provides considerable knowledge about the molecular regulation of astaxanthin biosynthesis and the existing research gap. Besides, it provides the basis for transcription factors mediated metabolic engineering of astaxanthin biosynthesis in H. pluvialis.

Numerical simulation of vortex flow field generated in a novel nested-bottled photobioreactor to improve Arthrospira platensis growth.

In this study, computational fluid dynamics were employed to examined clockwise and anticlockwise vortexes in the rising and down coming sections of novel nested-bottle photobioreactor. The radial velocity was increased by four times which significantly reduced dead zones compared to traditional PBR. The (NB-PBR) comprised of integrated bottles connected by curved tubes (d = 4 cm) that generated dominant vortices as the microalgae solution flows through each section (h = 10 cm). The (NB-PBR) was independent of the inner and outer sections which increased the mixing time and mass-transfer coefficient by 13.33 % and 42.9 %, respectively. Furthermore, the results indicated that the (NB-PBR) showed higher photosynthesis efficiency preventing self-shading and photo-inhibition, resulting in an increase in biomass yield and carbon dioxide fixation by 35 % and 35.9 %, respectively.

Magnetic/electric field intervention on oil-rich filamentous algae production in the application of acrylonitrile butadiene styrene based wastewater treatment.

Globally, the release of acrylonitrile-butadienestyrene (ABS) wastewater from numerous industries is a serious concern. Recently, oil-rich filamentous algae Tribonema sp has been grown utilizing toxic but nutrient-rich ABS effluent. Here, Tribonema sp. was cultivated under intervention of different magneto-electric combinatory fields (MCFs) (control, 0.6 V/cm, 1 h/d-1.2 V/cm, 1 h/d-0.6 V/cm, and 1 h/d-1.2 V/cm). Results showed MCF (1 h/d-0.6 V/cm) intervention increased the biomass by 9.7% (2.4 g/L) combined with high removal efficiencies (95% and 99%) of ammonium nitrogen and total phosphorus. The chemical oxygen demand (COD) removal rate increased to 82%, 6% higher than the control. Moreover, MCF of 1 h/d-0.6 V/cm significantly increased lipid and carbohydrate by 7.71% and 4.73% respectively. MCF increased premium fatty acid content such as palmitic acid (C16:0), myristic acid (C14: 0), and hexadecenoic acid (C16:1). MCF intervention also supported a diverse microbial flora, offering a favorable solution for ABS wastewater treatment.

Direct processing of alginate-immobilized microalgae into polyhydroxybutyrate using marine bacterium of Saccharophagus degradans.

Alginate immobilized microalgae (AIM) was found efficient in algal cells separation and pollutants removal, however, its processing required alginate removal. In present study, polysaccharide-degrading bacterium of Saccharophagus degradans was used to biodegrade alginate and microalgae in AIM and produce polyhydroxybutyrate (PHB). Results showed that AIM cultivated in wastewater contained 34.0% carbohydrate and 45.7% protein. S. degradans effectively degraded and utilized polysaccharide of AIM to maintain five-day continuous growth at 7.1-8.8 log CFU/mL. Compared with glucose, S. degradans metabolism of mixed polysaccharide in AIM maintained the medium pH at 7.1-7.8. Increasing the inoculum concentration did not enhance AIM utilization by S. degradans due to the carbon catabolite repression of glucose which likely inactivated hydrolysis enzymes. PHB production in S. degradans peaked at 64.9 mg/L after 72 h cultivation but was later degraded to provide energy. Conclusively, S. degradans was effective in direct processing of AIM while showing potential in PHB production.

Biomass production of carbohydrate-rich filamentous microalgae coupled with treatment and nutrients recovery from acrylonitrile butadiene styrene based wastewater: Synergistic enhancement with low carbon dioxide supply strategy.

This study attempted to remove acrylonitrile and acetophenone from simulated acrylonitrile butadiene styrene (ABS) based wastewater while recovering nitrogen and phosphorus using the carbohydrate-rich filamentous microalgae Tribonema sp.. Results showed that typical acetophenone and acrylonitrile presented significant inhibitory effect on Tribonema sp. growth and co-metabolism of CO2 improved the tolerance of Tribonema sp. to toxic pollutants. The microalgae biomass increased by 34.47% (3.16 g/L) and 58.17% (3.97 g/L) via supplementing 2% CO2 in the 100 mg/L acrylonitrile and acetophenone groups, respectively. The filamentous microalga was rich in carbohydrates and its productivity was further enhanced by 32.52% and 70.34%, respectively, in 100 mg/L acrylonitrile and acetophenone groups with 2% CO2 supplement. The synergistic CO2 supply strategy effectively enhanced the biomass production of filamentous microalgae, and moreover, improved the treatment efficiency of ABS based wastewater simulated by acetophenone or acrylonitrile addition, while at same time enhanced the recovery of nitrogen and phosphorus nutrients.

Weak magnetic field intervention on outdoor production of oil-rich filamentous microalgae: Influence of seasonal changes.

The weak magnetic field (MF) intervention on the semi-continuous system of filamentous algae Tribonema sp. during outdoor cultivation was investigated using starch wastewater. Results show that except for winter, MF in other seasons can effectively improve the algal biomass yield and oil productivity. In summer, the biomass concentration and oil productivity of Tribonema sp. could reach up to 14.7 g/L and 0.216 g/(L d) (130 mT), which increased by 9.8% and 35.8% respectively compared with the control group without MF intervention. By continuously shortening HRT to increase the nutrient load, the removal rate of COD, total nitrogen and total phosphorus all reached more than 87.9%. MF intervention not only weakened the bacterial diversity in open-photobioreactors system but also proved to be beneficial to the establishment of bacteria-algae symbiotic system. As a non-transgenic method, MF effectively up-regulated the growth of filamentous microalgae and promoted the biosynthesis productivity of high value-added compounds.

Integration of ozone with co-immobilized microalgae-activated sludge bacterial symbiosis for efficient on-site treatment of meat processing wastewater.

Direct discharge of high concentration meat processing wastewater (MPW) into municipal sewage system will cause serious shock loading and reduce wastewater treatment efficiency, thus, efficient on-site pretreatment is usually required. Purpose of this study is to integrate ozone with microalgal biotreatment to achieve effective removal of both organic compounds and nutrients with one-step biodegradation and obtain high quality effluent dischargeable to municipal sewage system. Results showed that ozone pretreatment removed 35.0-90.2% color and inactivated 1.8-4.7 log CFU/mL bacteria in MPW. In post biotreatment using microalgae co-immobilized with activated sludge (ACS) bacteria, bacterial growth in ozone pretreated wastewater (7.1-8.1 log CFU/mL) were higher than non-pretreated control (6.0 log CFU/mL) due to enhanced biodegradability of wastewater pollutants. Algal biomass growth in wastewater pretreated with 0.5 (2489.3 mg/L) and 1 (2582.0 mg/L) minute's ozonation were improved and higher than control (2297.1 mg/L). Ozone pretreatment significantly improved nutrients removal. Following ozone pretreatment of 0.5 min, microalgal biotreatment removed 60.1% soluble chemical oxygen demand (sCOD), 79.5% total nitrogen (TN) and 91.9% total phosphate (PO43-) which were higher than control (34.4% sCOD, 63.4% TN, 77.6% total PO43-). Treated effluent contained 342.3 mg/L sCOD, 28.8 mg/L TN, 9.9 mg/L total PO43- and could be discharged into municipal sewage system. However, excessive ozone pretreatment displayed adverse impact on algal growth and sCOD removal. Therefore, integration of 0.5 min's ozone pretreatment with microalgae-based biotreatment is an efficient on-site treatment to simultaneously remove organic compounds and nutrients with one-step biodegradation.

Integration of sodium hypochlorite pretreatment with co-immobilized microalgae/bacteria treatment of meat processing wastewater.

Wastewater with 0.2, 0.4, 0.8, 1.0 mg/L free chlorine was biologically treated using co-immobilized microalgae/bacteria. In contrast, non-pretreated wastewater was treated with beads (control) and blank beads (blank) under the same operating condition. Results showed that NaClO pretreatment removed 8-33% total nitrogen (TN), 31-45% true color and 0.7-2.5 log CFU/mL aerobic-bacteria. At the end of treatment, maximum algal biomass (2,027 dry weight mg/L) was achieved with 0.2 mg/L free chlorine. Bacterial growth in wastewater was decreased by NaClO pretreatment before reaching 7.2-7.7 log CFU/mL on the fifth day. Beads with microorganisms (control) removed 15% more chemical-oxygen-demand (COD), 16% more TN, and 13% more total phosphate (PO43-) than blank. Pretreatment with 0.2 mg/L free chlorine increased TN removal from 75% to 80% while pollutants removal was substantially decreased with 0.4-1.0 mg/L free chlorine. Considering algal biomass growth and pollutants removal, 0.2 mg/L free chlorine pretreatment was recommended for microalgae/bacteria co-immobilized system.