Revalorization of Microalgae Biomass for Synergistic Interaction and Sustainable Applications: Bioplastic Generation.

Microalgae and cyanobacteria are photosynthetic microorganisms' sources of renewable biomass that can be used for bioplastic production. These microorganisms have high growth rates, and contrary to other feedstocks, such as land crops, they do not require arable land. In addition, they can be used as feedstock for bioplastic production while not competing with food sources (e.g., corn, wheat, and soy protein). In this study, we review the macromolecules from microalgae and cyanobacteria that can serve for the production of bioplastics, including starch and glycogen, polyhydroxyalkanoates (PHAs), cellulose, polylactic acid (PLA), and triacylglycerols (TAGs). In addition, we focus on the cultivation of microalgae and cyanobacteria for wastewater treatment. This approach would allow reducing nutrient supply for biomass production while treating wastewater. Thus, the combination of wastewater treatment and the production of biomass that can serve as feedstock for bioplastic production is discussed. The comprehensive information provided in this communication would expand the scope of interdisciplinary and translational research.

Implementation of kLa-Based Strategy for Scaling Up Porphyridium purpureum (Red Marine Microalga) to Produce High-Value Phycoerythrin, Fatty Acids, and Proteins.

Porphyridium purpureum is a well-known Rhodophyta that recently has attracted enormous attention because of its capacity to produce many high-value metabolites such as the pigment phycoerythrin and several high-value fatty acids. Phycoerythrin is a fluorescent red protein-pigment commercially relevant with antioxidant, antimicrobial activity, and fluorescent properties. The volumetric mass transfer coefficient (kLa) was kept constant within the different scaling-up stages in the present study. This scaling-up strategy was sought to maintain phycoerythrin production and other high-value metabolites by Porphyridium purpureum, using hanging-bag photobioreactors. The kLa was monitored to ensure the appropriate mixing and CO2 diffusion in the entire culture during the scaling process (16, 80, and 400 L). Then, biomass concentration, proteins, fatty acids, carbohydrates, and phycoerythrin were determined in each step of the scaling-up process. The kLa at 16 L reached a level of 0.0052 s-1, while at 80 L, a value of 0.0024 s-1 was achieved. This work result indicated that at 400 L, 1.22 g L-1 of biomass was obtained, and total carbohydrates (117.24 mg L-1), proteins (240.63 mg L-1), and lipids (17.75% DW) were accumulated. Regarding fatty acids production, 46.03% palmitic, 8.03% linoleic, 22.67% arachidonic, and 2.55% eicosapentaenoic acid were identified, principally. The phycoerythrin production was 20.88 mg L-1 with a purity of 2.75, making it viable for food-related applications. The results of these experiments provide insight into the high-scale production of phycoerythrin via the cultivation of P. purpureum in an inexpensive and straightforward culture system.

Influence of Low Salt Concentration on Growth Behavior and General Biomass Composition in Lyngbya purpurem (Cyanobacteria).

Cyanobacteria are essential for the vast number of compounds they produce and the possible applications in the pharmaceutical, cosmetical, and food industries. As Lyngbya species' characterization is limited in the literature, we characterize this cyanobacterium's growth and biomass. L. purpureum was grown and analyzed under different salinities, culture media, and incubation times to determine the best conditions that favor its cell growth and the general production of proteins, carbohydrates, lipids, and some pigments as phycocyanin and chlorophyll a. In this study, each analyzed biomolecule's highest content was proteins 431.69 mg g-1, carbohydrates 301.45 mg g-1, lipids 131.5 mg g-1, chlorophyll a 4.09 mg g-1, and phycocyanin 40.4 mg g-1. These results can provide a general context of the possible uses that can be given to biomass and give an opening to investigate possible biocompounds or bio metabolites that can be obtained from it.

Removal and biotransformation of 4-nonylphenol by Arthrospira maxima and Chlorella vulgaris consortium.

4-Nonylphenol (4-NP) is an anthropogenic contaminant found in different environmental matrices that has an effect over the biotic and abiotic factors within the environment. Bioremediation by microorganisms can be used as a potential treatment to remove this pollutant. In this work, a consortium of two microorganisms, Arthrospira maxima and Chlorella vulgaris, was employed to remove 4-NP from water. The parameters analyzed included cell growth, removal of 4-NP, and 4-NP remnant in the biomass. In addition, the metabolites produced in the process by this consortium were identified. It was found that C. vulgaris is more resistant to 4-NP than A. maxima (cell growth inhibition by 4-NP of 99%). The consortium used in this study had an IC50 greater than any strain of microalgae or cyanobacteria reported for 4-NP removal (9.29 mg/L) and reduced up to 96% of 4-NP in water in the first 48 h of culture. It was also observed that there is a bio-transformation of 4-NP, comparable with the process carried out by another bacterium, in which three similar metabolites were found (4-(1-methyl-octyl)-4-hydroxy-cyclohex-2-enone, 4-nonyl-4-hydroxy-ciclohexa-2,5-dienone and 4-nonyl-4-hydroxy- ciclohex-2-enone) and one that is similar to plant metabolism (4-nonyl-(1-methyl,6,8-metoxy)-hydroxybenzene). These results indicate that microalgae and cyanobacteria consortium can be used to remove 4-NP from water.

Light Intensity and Nitrogen Concentration Impact on the Biomass and Phycoerythrin Production by Porphyridium purpureum.

Several factors have the potential to influence microalgae growth. In the present study, nitrogen concentration and light intensity were evaluated in order to obtain high biomass production and high phycoerythrin accumulation from Porphyridium purpureum. The range of nitrogen concentrations evaluated in the culture medium was 0.075-0.450 g L-1 and light intensities ranged between 30 and 100 µmol m-2 s-1. Surprisingly, low nitrogen concentration and high light intensity resulted in high biomass yield and phycoerythrin accumulation. Thus, the best biomass productivity (0.386 g L-1 d-1) and biomass yield (5.403 g L-1) were achieved with NaNO3 at 0.075 g L-1 and 100 µmol m-2 s-1. In addition, phycoerythrin production was improved to obtain a concentration of 14.66 mg L-1 (2.71 mg g-1 of phycoerythrin over dry weight). The results of the present study indicate that it is possible to significantly improve biomass and pigment production in Porphyridium purpureum by limiting nitrogen concentration and light intensity.

CO2 biocapture by Scenedesmus sp. grown in industrial wastewater.

Greenhouse gases (GHG) emissions are widely related to climate change, triggering several environmental problems of global concern and producing environmental, social, and economic negative impacts. Therefore, global research seeks to mitigate greenhouse gas emissions. On the other hand, the use of wastes under a circular economy scheme generates subproducts from the range of high to medium-value, representing a way to help sustainable development. Therefore, the use of wastewater as a culture medium to grow microalgae strains that biocapture environmental CO2, is a proposal with high potential to reduce the GHG presence in the environment. In this work, Scenedesmus sp. was cultivated using BG-11 medium and industrial wastewater (IWW) as a culture medium with three different CO2 concentrations, 0.03%, 10%, and 20% to determine their CO2 biocapture potential. Furthermore, the concomitant removal of COD, nitrates, and total phosphorus in wastewater was evaluated. Scenedesmus sp. achieves a biomass concentration of 1.9 g L-1 when is grown in BG-11 medium, 0.69 g L-1 when is grown in a combination of BG-11 medium and 25% of industrial wastewater; both cases with 20% CO2 supplied. The maximum CO2 removal efficiency (8.4%, 446 ± 150 mg CO2 L-1 day-1) was obtained with 10% CO2 supplied and using a combination of BG-11 medium and 50% IWW (T2). Also, the highest removal of COD was reached with a combination of BG-11 medium and T2 with a supply of 20% CO2 (82% of COD removal). Besides, the highest nitrates removal was achieved with a combination of BG-11 medium and 75% IWW (T3) with a supply of 10% CO2 (42% of nitrates removal) and the maximum TP removal was performed with the combination of BG-11 medium and 25% IWW (T1) with a supply of 10% CO2 (67% of TP removal). These results indicate that industrial wastewater can be used as a culture media for microalgae growth and CO2 biocapture can be performed as concomitant processes.

Sources of antibiotics pollutants in the aquatic environment under SARS-CoV-2 pandemic situation.

During the last decades, the growth of concern towards different pollutants has been increasing due to population activities in large cities and the great need for food production by the agri-food industry. The effects observed in specific locations have shown the impact over the environment in air, soil and water. Specifically, the current pandemic of COVID-19 has brought into the picture the intensive use of different medical substances to treat the disease and population intensive misuse. In particular, the use of antibiotics has increased during the last 20 years with few regulations regarding their excessive use and the disposal of their residues from different sources. Within this review, an overview of sources of antibiotics to aquatic environments was done along with its impact to the environment and trophic chain, and negative effects of human health due prolonged exposure which endanger the environment, population health, water, and food sustainability. The revision indicates the differences between sources and its potential danger due toxicity, and accumulation that prevents water sustainability in the long run.

Accumulation of PHA in the Microalgae Scenedesmus sp. under Nutrient-Deficient Conditions.

Traditional plastics have undoubted utility and convenience for everyday life; but when they are derived from petroleum and are non-biodegradable, they contribute to two major crises today's world is facing: fossil resources depletion and environmental degradation. Polyhydroxyalkanoates are a promising alternative to replace them, being biodegradable and suitable for a wide variety of applications. This biopolymer accumulates as energy and carbon storage material in various microorganisms, including microalgae. This study investigated the influence of glucose, N, P, Fe, and salinity over the production of polyhydroxyalkanoate (PHA) by Scenedesmus sp., a freshwater microalga strain not previously explored for this purpose. To assess the effect of the variables, a fractional Taguchi experimental design involving 16 experimental runs was planned and executed. Biopolymer was obtained in all the experiments in a wide range of concentrations (0.83-29.92%, w/w DW), and identified as polyhydroxybutyrate (PHB) by FTIR analysis. The statistical analysis of the response was carried out using Minitab 16, where phosphorus, glucose, and iron were identified as significant factors, together with the P-Fe and glucose-N interactions. The presence of other relevant macromolecules was also quantified. Doing this, this work contributes to the understanding of the critical factors that control PHA production and present Scenedesmus sp. as a promising species to produce bio-resources in commercial systems.