Exploring effective light spectral conversion techniques for enhanced production of Spirulina-derived blue pigment protein, c-phycocyanin.

Spirulina is a promising feedstock for c-phycocyanin, a blue pigment-protein, commercially incorporated in many food products for its desirable bright blue attributes, exceptional bioavailability, and inherent therapeutic properties. Remarkably, enhancing c-phycocyanin synthesis in Spirulina would facilitate economic viability and sustainability at large-scale production, as the forecasted market value is $ 409.8 million by 2030. Notably, the lighting source plays a key role in enhancing c-phycocyanin in Spirulina, and thus, strategies to filter/concentrate the photons of respective wavelengths, influencing light spectra, are beneficial. Enveloping open raceway ponds and greenhouses by luminescent solar concentrators and light filtering sheets enables solar spectral conversion of the sunlight at desirable wavelengths, emerges as a promising strategy to enhance synthesis of c-phycocyanin in Spirulina. Nevertheless, the conduction of techno-economic assessments and evaluation of scalability at large-scale cultivation of Spirulina are essential for the real-time implementation of lighting strategies.

Modeling of astaxanthin biosynthesis via machine learning, mathematical and metabolic network modeling.

Natural astaxanthin is synthesized by diverse organisms including: bacteria, fungi, microalgae, and plants involving complex cellular processes, which depend on numerous interrelated parameters. Nonetheless, existing knowledge regarding astaxanthin biosynthesis and the conditions influencing astaxanthin accumulation is fairly limited. Thus, manipulation of the growth conditions to achieve desired biomass and astaxanthin yields can be a complicated process requiring cost-intensive and time-consuming experiment-based research. As a potential solution, modeling and simulation of biological systems have recently emerged, allowing researchers to predict/estimate astaxanthin production dynamics in selected organisms. Moreover, mathematical modeling techniques would enable further optimization of astaxanthin synthesis in a shorter period of time, ultimately contributing to a notable reduction in production costs. Thus, the present review comprehensively discusses existing mathematical modeling techniques which simulate the bioaccumulation of astaxanthin in diverse organisms. Associated challenges, solutions, and future perspectives are critically analyzed and presented.

A novel two-stage process for the effective treatment of swine wastewater using Chlorella sorokiniana AK-1 based algal-bacterial consortium under semi-continuous operation.

This study aimed at developing an eco-friendly and effective treatment for swine wastewater (SWW) using a designer microalgae-bacteria consortium. A functional algal bacterial consortium was developed with SWW-derived bacteria and Chlorella sorokiniana AK-1. Light intensity (300 µmol/m2/s) and inoculum size (0.15 and 0.2 g/L for microalgae and bacteria) were optimized. Semi-batch operation treating 50 % SWW resulted in a COD, BOD, TN, and TP removal efficiency of 81.1 ± 0.9 %, 97.0 ± 0.7 %, 90.6 ± 1.6 % and 91.3 ± 1.1 %, respectively. A novel two-stage process with an initial bacterial start-up stage followed by microalgal inoculation was applied for attaining stable organic carbon removal, in addition to satisfactory TN and TP removal. Full strength SWW was treated with this strategy with COD, BOD, TN, and TP removal efficiencies of 72.1 %, 94.9 %, 88 %, and 94.6 %, respectively. The biomass consisted of 36 % carbohydrates, indicating a potential feedstock for biochar production. In addition, the effluent met the standards for effluent discharge in Taiwan.

Macroalgal biomass as a potential resource for lactic acid fermentation.

Lactic acid is an essential platform chemical with various applications in the chemicals, food, pharmaceutical, and cosmetic industries. Currently, the demand for lactic acid is driven by the role of lactic acid as the starting material for the production of bioplastic polylactide. Microbial fermentation for lactic acid production is favored due to the production of enantiomerically pure lactic acid required for polylactide synthesis, as opposed to the racemic mixture obtained via chemical synthesis. The utilization of first-generation feedstock for commercial lactic acid production is challenged by feedstock costs and sustainability issues. Macroalgae are photosynthetic benthic aquatic plants that contribute tremendously towards carbon capture with subsequent carbon-rich biomass production. Macroalgae are commercially cultivated to extract hydrocolloids, and recent studies have focused on applying biomass as a fermentation feedstock. This review provides comprehensive information on the design and development of sustainable and cost-effective, algae-based lactic acid production. The central carbon regulation in lactic acid bacteria and the metabolism of seaweed-derived sugars are described. An exhaustive compilation of lactic acid fermentation of macroalgae hydrolysates revealed that lactic acid bacteria can effectively ferment the mixture of sugars present in the hydrolysate with comparable yields. The environmental impacts and economic prospects of macroalgal lactic acid are analyzed. Valorization of the vast amounts of spent macroalgal biomass residue post hydrocolloid extraction in a biorefinery is a viable strategy for cost-effective lactic acid production.

Novel strategy for microalgae cell disruption and wet lipid extraction by employing electro-Fenton process with sacrificial steel anode.

Electro-Fenton process (EFP) was studied as a potential cell disruption technique for recovery of lipids from wet biomass of the microalga Chlorella homosphaera. A novel approach of electrochemical dissolution of a sacrificial steel anode was used to provide Fe2+ required to initiate EFP and microalgae cell disruption. Response surface methodology (RSM) was employed to optimize the process parameters and maximize the lipid yield of EFP. The RSM model (R2 = 90.66%, Adj.R2 = 87.71%) showed that a maximum lipid yield of 18.29% could be obtained at 40 min reaction time and 4.38 g/L biomass concentration. Experimental validation resulted in a lipid yield of 19.99 ± 1.33%, which was significantly higher than wet lipid extraction without cell disruption. However, the lipid yield of EFP should be further improved to achieve comparable results to mechanical cell disruption methods. Nonetheless, biodiesel synthesized from lipids obtained via EFP conformed to the ASTM D6751-12 standard.

Wastewater-based microalgal biorefineries for the production of astaxanthin and co-products: Current status, challenges and future perspectives.

The freshwater microalgae Haematococcus pluvialis and Chlorella zofingiensis are attractive biorefinery feedstocks in view of their ability to simultaneously synthesize astaxanthin and other valuable metabolites. Nonetheless, there are concerns regarding the sustainability of such biorefineries due to the high freshwater footprint of microalgae cultivation. The integration of wastewater as an alternative growth media is a promising approach to reduce freshwater demand. Wastewater-based cultivation enables the recovery of essential nutrients required for microalgae growth and consequently results in phycoremediation of wastewater, thus promoting the concept of a circular economy and further enhancing the sustainability of the process. In this review, recent developments in wastewater-integrated cultivation of H. pluvialis and C. zofingiensis for astaxanthin production are discussed. Furthermore, prospective strategies for overcoming the inherent challenges of wastewater-based cultivation are reviewed. Moreover, the biorefinery potential of wastewater-grown H. pluvialis and C. zofingiensis is delineated and future perspectives of wastewater-based biorefineries are outlined.

Yeast assisted algal flocculation for enhancing nutraceutical potential of Chlorella pyrenoidosa.

The present research describes yeast assisted algal flocculation followed by evaluation of algae-yeast flocs for nutritional profile as potent food product. Co-flocculation of Chlorella pyrenoidosa using Saccharomyces cerevisiae showed 58.33 ± 2.37% flocculation efficiency. Nutrient composition of algae-yeast flocs (CP-Y) depicted higher protein content (35.52%) as compared to algae (23.72%) and yeast biomass (33.89). Amino acid profiles of CP-Y biomass depicted increase in essential amino acid content with higher ratio of essential to non-essential amino acid (0.68) as compared to Y (0.57) and CP (0.57) biomass. Lipid and carbohydrate content of CP-Y flocs was estimated as 26.95 ± 0.57% and 21.12 ± 0.83%, respectively. Fatty Acid Methyl Esters (FAME) analysis showed presence of omega rich polyunsaturated fatty acids (PUFAs) like α-linolenic acid (ω-3), Linoleic acid (ω-6), Palmitoleic acid (ω-7) etc in CP-Y biomass. The study provides novel insights on nutrition enriched biomass obtained after algal-yeast flocculation, which can be a better alternative to existing flocculation methods for food applications.

Biological decolourization of textile industry wastewater by a developed bacterial consortium.

Most currently employed textile effluent decolourization methods use physical and chemical processes where dyes do not get degraded instead concentrated or transferred into a solid phase. Therefore, further treatment processes are required to destroy dyes from the environment. In contrast, biological decolourization may result in degradation of the dye structure due to microbial activities and hence biological processes can be considered environmentally friendly. In the present study, bacterial strains with dye decolourization potential were isolated from the natural environment and their ability to decolourize four different reactive textile dyes was studied individually and in a bacterial consortium. The developed bacterial consortium composed with Proteus mirabilis, Morganella morganii and Enterobacter cloacae indicated more than 90% color removals for all four dyes and optimum decolourization of the dye mixture was observed at 40 °C and pH 7. The developed bacterial consortium decolourized 60% of dyes in textile industry effluent at 35 °C and pH 7 showing their ability to endure in highly complex and toxic environments and application in textile industry wastewaters.

Comparative assessment on the extraction of carotenoids from microalgal sources: Astaxanthin from H. pluvialis and ß-carotene from D. salina.

Astaxanthin and ß-carotene are important carotenoids used in numerous pharmaceutical and nutraceutical applications, owing to their vigorous antioxidant properties. The microalgal strains Haematococcus pluvialis and Dunaliella salina accumulate the highest quantities of astaxanthin and ß-carotene (up to 7% and 13% dry weight respectively) and are therefore considered as sustainable feedstock for the commercial production of carotenoids. Thus, from an economical perspective, it becomes desirable to optimize recovery of carotenoids from microalgal cells. To this end, here, we have summarized the conventional and modern extraction techniques generally used for the recovery of astaxanthin from Haematococcus pluvialis and ß-carotene from Dunaliella salina. Furthermore, we have also discussed the optimum process conditions employed for numerous extraction protocols including solvent extraction, ultrasonic-assisted extraction (UAE), microwave-assisted extraction (MAE) and supercritical fluid extraction (SFE). Overall, our study highlights the sustainability of integrated co-production of biofuels and carotenoids in a biorefinery framework.

OsCBSCBSPB4 is a Two Cystathionine-ß-Synthase Domain-containing Protein from Rice that Functions in Abiotic Stress Tolerance.

Cystathionine ß-synthase (CBS) domains have been identified in a wide range of proteins of unrelated functions such as, metabolic enzymes, kinases and channels, and usually occur as tandem re-peats, often in combination with other domains. In plants, CBS Domain-Containing Proteins (CDCPs) form a multi-gene family and only a few are so far been reported to have a role in development via regu-lation of thioredoxin system as well as in abiotic and biotic stress response. However, the function of majority of CDCPs still remains to be elucidated in plants. Here, we report the cloning, characterization and functional validation of a CBS domain containing protein, OsCBSCBSPB4 from rice, which pos-sesses two CBS domains and one PB1 domain. We show that OsCBSCBSPB4 encodes a nucleo-cytoplasmic protein whose expression is induced in response to various abiotic stress conditions in salt-sensitive IR64 and salt-tolerant Pokkali rice cultivars. Further, heterologous expression of OsCBSCB-SPB4 in E. coli and tobacco confers marked tolerance against various abiotic stresses. Transgenic tobac-co seedlings over-expressing OsCBSCBSPB4 were found to exhibit better growth in terms of delayed leaf senescence, profuse root growth and increased biomass in contrast to the wild-type seedlings when subjected to salinity, dehydration, oxidative and extreme temperature treatments. Yeast-two hybrid stud-ies revealed that OsCBSCBSPB4 interacts with various proteins. Of these, some are known to be in-volved in abiotic stress tolerance. Our results suggest that OsCBSCBSPB4 is involved in abiotic stress response and is a potential candidate for raising multiple abiotic stress tolerant plants.

Expression of abiotic stress inducible ETHE1-like protein from rice is higher in roots and is regulated by calcium.

ETHYLMALONIC ENCEPHALOPATHY PROTEIN 1 (ETHE1) encodes sulfur dioxygenase (SDO) activity regulating sulfide levels in living organisms. It is an essential gene and mutations in ETHE1 leads to ethylmalonic encephalopathy (EE) in humans and embryo lethality in Arabidopsis. At present, very little is known regarding the role of ETHE1 beyond the context of EE and almost nothing is known about factors affecting its regulation in plant systems. In this study, we have identified, cloned and characterized OsETHE1, a gene encoding ETHE1-like protein from Oryza sativa. ETHE1 proteins in general are most similar to glyoxalase II (GLYII) and hence OsETHE1 has been earlier annotated as OsGLYII1, a putative GLYII gene. Here we show that OsETHE1 lacks GLYII activity and is instead an ETHE1 homolog being localized in mitochondria like its human and Arabidopsis counterparts. We have isolated and analyzed 1618 bp OsETHE1 promoter (pOsETHE1) to examine the factors affecting OsETHE1 expression. For this, transcriptional promoter pOsETHE1: 5-bromo-5-chloro-3-indolyl-ß-D-glucuronide (GUS) fusion construct was made and stably transformed into rice. GUS expression pattern of transgenic pOsETHE1:GUS plants reveal a high root-specific expression of OsETHE1. The pOsETHE1 activity was stimulated by Ca(II) and required light for induction. Moreover, pOsETHE1 activity was induced under various abiotic stresses such as heat, salinity and oxidative stress, suggesting a potential role of OsETHE1 in stress response.