The Response of Extracellular Polymeric Substances Production by Phototrophic Biofilms to a Sequential Disturbance Strongly Depends on Environmental Conditions

Phototrophic biofilms are exposed to multiple stressors that can affect them both directly and indirectly. By modifying either the composition of the community or the physiology of the microorganisms, press stressors may indirectly impact the ability of the biofilms to cope with disturbances. Extracellular polymeric substances (EPS) produced by the biofilm are known to play an important role in its resilience to various stresses. The aim of this study was to decipher to what extent slight modifications of environmental conditions could alter the resilience of phototrophic biofilm EPS to a realistic sequential disturbance (4-day copper exposure followed by a 14-day dry period). By using very simplified biofilms with a single algal strain, we focused solely on physiological effects. The biofilms, composed by the non-axenic strains of a green alga (Uronema confervicolum) or a diatom (Nitzschia palea) were grown in artificial channels in six different conditions of light intensity, temperature and phosphorous concentration. EPS quantity (total organic carbon) and quality (ratio protein/polysaccharide, PN/PS) were measured before and at the end of the disturbance, and after a 14-day rewetting period. The diatom biofilm accumulated more biomass at the highest temperature, with lower EPS content and lower PN/PS ratio while green alga biofilm accumulated more biomass at the highest light condition with lower EPS content and lower PN/PS ratio. Temperature, light intensity, and P concentration significantly modified the resistance and/or recovery of EPS quality and quantity, differently for the two biofilms. An increase in light intensity, which had effect neither on the diatom biofilm growth nor on EPS production before disturbance, increased the resistance of EPS quantity and the resilience of EPS quality. These results emphasize the importance of considering the modulation of community resilience ability by environmental conditions, which remains scarce in the literature.

Identification of a New Microalgal Strain From Chromite Mine Wastes for Detoxification of Hexavalent Chromium for Sustainable Crop Growth

Sukinda chromium mine is well known for its chromium (Cr) reserve in India. It accounts for 97% of Cr production in the country. The open cast mining results in the seepage and accumulation of chromium in the nearby paddy fields through soil runoff. Deposition of high concentrations of toxic Cr6+ adversely affected the growth and productivity of rice plants. It was studied that Cr6+ toxicity can be counteracted by the microbes especially algae. Hence, an attempt has been made for the exploration of an indigenous micro-algal strain for the detoxification of Cr6+ in the rice fields. Three different micro-algal strains were isolated from the waterlogged regions of the mine waste area and tested against Cr6+. The average concentration of Cr6+ in the soils of rice fields and its surrounding regions was estimated around 40ppm. In vitro study was conducted to determine the optimal growth parameters for the growth of the algal strains. The concentration of total chromium availability was determined by using ICP-OES (Inductively coupled plasma atomic emission spectroscopy. It showed that all the algal-stains were able to detoxify Cr6+, but the best result (89.63%) was observed in one strain ‘SM3’. SEM-EDX study also showed that there was no Cr adsorbed on the surface of the algal strain. Raman Spectroscopy study confirmed the reduction of Cr6+ to Cr3+ in algal strain. The strain was identified as Fischerella sp. (Accession no. MK422171) through morphological and molecular characterization. This algal strain can be used for the bioremediation of chromium contaminated crop fields.

Algal glycobiotechnology: omics approaches for strain improvement

Microalgae has the capability to replace petroleum-based fuels and is a promising option as an energy feedstock because of its fast growth, high photosynthetic capacity and remarkable ability to store energy reserve molecules in the form of lipids and starch. But the commercialization of microalgae based product is difficult due to its high processing cost and low productivity. Higher accumulation of these molecules may help to cut the processing cost. There are several reports on the use of various omics techniques to improve the strains of microalgae for increasing the productivity of desired products. To effectively use these techniques, it is important that the glycobiology of microalgae is associated to omics approaches to essentially give rise to the field of algal glycobiotechnology. In the past few decades, lot of work has been done to improve the strain of various microalgae such as Chlorella, Chlamydomonas reinhardtii, Botryococcus braunii etc., through genome sequencing and metabolic engineering with major focus on significantly increasing the productivity of biofuels, biopolymers, pigments and other products. The advancements in algae glycobiotechnology have highly significant role to play in innovation and new developments for the production algae-derived products as above. It would be highly desirable to understand the basic biology of the products derived using -omics technology together with biochemistry and biotechnology. This review discusses the potential of different omic techniques (genomics, transcriptomics, proteomics, metabolomics) to improve the yield of desired products through algal strain manipulation.

Selection of Indigenous Algal Species for Potential Biodiesel Production

Currently, India utilizes an enormous amount of fossil fuels and a major quantity of fossil fuels are imported from other countries. It’s a giant load on the Indian Economy. The burning of fossil fuels causes global warming. Carbon neutral, renewable fuels are essential for environmental protection and it’s economically sustainable for India. Biofuels attention day by day due to a rise in energy demands and environmental concerns. Biodiesel produced from algal oil a possible renewable and carbon-neutral substitute to fossil fuels. The feasibility of the algal-based biodiesel industry depends on the selection of adequate species regarding commercial oil yields and oil quality. Present research work to bioprospecting and screening of 19 algal and blue-green algal species, the oil percentage and the fatty acid profiles, used for analyzing the biodiesel fuel properties. Oil from Tolypothrix phyllophila algal strain and compared it with another eighteen algal and blue-green algal strains from different literature. Tolypothrix phyllophila algal strain contains approximately 12.6% lipid on a dry weight basis. We also compared the FAME profile of 19 algal and blue-green algal strains and calculated and compared the fuel properties such as cetane number, Iodine Value, etc. of the biodiesel derived from these algal and blue-green algal oils based on chain length and saturation. We also investigated the 19 algal and blue-green algal fatty acid profiles and its suitability for biodiesel production and strains selection through PROMETHEE (Preference Ranking Organization Method for Enrichment Evaluations) and GAIA (geometrical analysis for interactive aid) analysis.

Using seawater-based Na2CO3 medium for scrubbing the CO2 released from Bio-CNG plant for enhanced biomass production of Pseudanabaena limnetica

The concentration of CO2, one of the most important greenhouse gases (GHG), has reached to 409.8 ± 0.1 ppm in 2019. Although there are many carbon capture and storage (CCS) methods, they are very costly and their long term use raises concern about environmental safety. Alternatively, bio-sequestration of CO2 using microalgal cell factories has emerged as a promising way of recycling CO2 into biomass via photosynthesis. In the present study, Indigenous algal strain Pseudanabaena limnetica was cultivated in pneumatically agitated 60-L flat-panel photobioreactor system. The gas was released from Bio-CNG plant as by-product into Na2CO3-rich medium and cultivated in semicontinuous mode of operation. It was observed that when CO2 was sparged in seawater-based 0.02 M Na2CO3 solution, maximum CO2 was dissolved in the system and was used for algal cultivation. Control system produced 0.64 ± 0.035 g/L of biomass at the end of 15 days, whereas CO2 sparged Na2CO3 medium produced 0.81 ± 0.046 g/L of biomass. When CO2 from Bio-CNG station was fed, it resulted in biomass production of 1.62 ± 0.070 g/L at the end of 18 days compared to 1.46 ± 0.066 g/L of biomass produced in control system which was not fed with gas released from Bio-CNG plant as by-product. Thus, feeding CO2 directly into Na2CO3 medium and operating the system semicontinuously would be efficient for scrubbing CO2 from commercial Bio-CNG plant. This study proves that feeding CO2 gas from Bio-CNG plant into Na2CO3-rich alkaline system can be used to feed algae for enhanced biomass production.

Comparison of Botryococcus braunii and Neochloris vigensis Biofilm Formation on Vertical Oriented Surfaces

Biofilm technology is a cost-effective process for microalgae biomass production. Materials can be successfully used as microalgae biomass adhesion carriers. The productivity of two different microalgal strains, Neochloris vigensis, and Botryococcus braunii, were compared in an opened pond system on eleven different surfaces (cork, sponge towel, denim, plexiglass, stainless steel, silicone rubber, glass, geotextile, and three different patterned plexiglass). Biomass attachment on the various materials was monitored for 16 days of cultivation. Various parameters were tested during cultivation, such as pH, cell concentration, chl-a, NO3-, PO43-, lipids, total proteins, and carbohydrates. Contact angle and surface energy were used to determine the surface characteristics. Plexiglass resulted in the best performance in the case of B.braunii (28.3 g/m2), while in the case of N.vigensis, sponge towel exhibited the highest productivity (17.8 g/m2). Based on the results, the algal strain affects the attachment, and hydrophilic materials can be as efficient as hydrophobic ones.