A novel integrated approach employing Desertifilum tharense BERC-3 for efficient wastewater valorization and recycling for developing peri-urban algae farming system.

Peri-urban environments are significant reservoirs of wastewater, and releasing this untreated wastewater from these resources poses severe environmental and ecological threats. Wastewater mitigation through sustainable approaches is an emerging area of interest. Algae offers a promising strategy for carbon-neutral valorization and recycling of urban wastewater. Aiming to provide a proof-of-concept for complete valorization and recycling of urban wastewater in a peri-urban environment in a closed loop system, a newly isolated biocrust-forming cyanobacterium Desertifilum tharense BERC-3 was evaluated. Here, the highest growth and lipids productivity were achieved in urban wastewater compared to BG11 and synthetic wastewater. D. tharense BERC-3 showed 60-95% resource recovery efficiency and decreased total dissolved solids, chemical oxygen demand, biological oxygen demand, nitrate nitrogen, ammonia nitrogen and total phosphorus contents of the water by 60.37%, 81.11%, 82.75%, 87.91%, 85.13%, 85.41%, 95.87%, respectively, making it fit for agriculture as per WHO's safety limits. Soil supplementation with 2% wastewater-cultivated algae as a soil amender, along with its irrigation with post-treated wastewater, improved the nitrogen content and microbial activity of the soil by 0.3-2.0-fold and 0.5-fold, respectively. Besides, the availability of phosphorus was also improved by 1.66-fold. The complete bioprocessing pipeline offered a complete biomass utilization. This study demonstrated the first proof-of-concept of integrating resource recovery and resource recycling using cyanobacteria to develop a peri-urban algae farming system. This can lead to establishing wastewater-driven algae cultivation systems as novel enterprises for rural migrants moving to urban areas.

Non-photochemical quenching in the cells of the carotenogenic chlorophyte Haematococcus lacustris under favorable conditions and under stress.

The microalga Haematococcus lacustris (formerly H. pluvialis) is the richest source of the valuable pigment astaxanthin, accumulated in red aplanospores (haematocysts). In this work, we report on the photoprotective mechanisms in H. lacustris, conveying this microalga its ability to cope with a wide range of adverse conditions, with special emphasis put on non-photochemical quenching (NPQ) of the excited chlorophyll states. We studied the changes in the primary photochemistry of the photosystems (PS) as a function of irradiance and the physiological state. We leveraged the transcriptomic data to gain a deeper insight into possible NPQ mechanisms in this microalga. Peculiar to H. lacustris is a bi-phasic pattern of changes in photoprotection during haematocyst formation. The first phase coincides with a transient rise of photosynthetic activity. Based on transcriptomic data, high NPQ level in the first phase is maintained predominantly by the expression of PsbS and LhcsR proteins. Then, (in mature haematocysts), stress tolerance is achieved by optical shielding by astaxanthin and dramatic reduction of photosynthetic apparatus. In contrast to many microalgae, shielding plays an important role in H. lacistris haematocysts, whereas regulated NPQ is suppressed. Astaxanthin is decoupled from the PS, hence the light energy is not transferred to reaction centers and dissipates as heat. It allows to retain a higher photochemical yield in haematocysts comparing to vegetative cells. The ability of H. lacustris to substitute the "classical" active photoprotective mechanisms such as NPQ with optic shielding and general metabolism quiescence makes this organism a useful model to reveal photoprotection mechanisms.

"Noah's Ark" Project: Interim Results and Outlook for Classic Collection Development.

The "Noah's Ark" project, afoot at M.V. Lomonosov Moscow State University since 2015 and aimed at studying biodiversity, is the largest ongoing Russian project in life sciences. During its implementation, several hundred new species have been described; a comprehensive genetic and biochemical characterization of these species, as well as that of the pre-existing specimens in Moscow University's collections, has been performed. A consolidated IT system intended to house the knowledge generated by the project has been developed. Here, we summarize the investigations around the Moscow University classical biocollections which have taken place within the framework of the project and discuss future promise and the outlook for these collections.

Effects of CO2 enrichment on primary photochemistry, growth and astaxanthin accumulation in the chlorophyte Haematococcus pluvialis.

The atmospheric CO2 level is limiting for growth of phototrophic organisms such as microalgae, so CO2 enrichment boosts the growth and photosynthesis of microalgal cultures. Still, excessive CO2 injection might inhibit photosynthesis of microalgae. We investigated the effect of continuous sparging of the cultures of Haematococcus pluvialis BM 1 (IPPAS H-2018) (Chlorophyceae), the richest natural source of the value-added pigment astaxanthin. H. pluvialis cultures with CO2-enriched air-gas mixtures (with CO2 level from the atmospheric to 20%) on growth and astaxanthin accumulation in the microalga. Special attention was paid to photosynthetic activity and non-photochemical excited chlorophyll states quenching in the microalgal cells, which was monitored via chlorophyll fluorescence analysis. We also report on the capability of CO2 capture by H. pluvialis derived from direct measurements of its elemental carbon content. The beneficial effect of the moderately high (5%) CO2 levels on the culture growth and astaxanthin accumulation under stress results in a higher overall astaxanthin productivity. However, increase of the CO2 level to 10% or 20% was deteriorative for growth, photosynthesis and carbon assimilation. The results support the possibility of combining a traditional two-stage H. pluvialis cultivation with CO2 bio-capture although a dilution of the flue gas before its injection is required.

Analysis of Photoprotection and Apparent Non-photochemical Quenching of Chlorophyll Fluorescence in Tradescantia Leaves Based on the Rate of Irradiance-Induced Changes in Optical Transparence.

The kinetics of irradiation-induced changes in leaf optical transparence (ΔT) and non-photochemical quenching (NPQ) of chlorophyll fluorescence in Tradescantia fluminensis and T. sillamontana leaves adapted to different irradiance in nature was analyzed. Characteristic times of a photoinduced increase and a dark decline of ΔT in these species were 12 and 20 min, respectively. The ΔT was not confirmed to be the main contributor to the observed middle phase of NPQ relaxation kinetics (τ = 10-28 min). Comparison of rate of photoinduced increase in ΔT and photosystem II quantum yield recovery showed that the former did not affect the tolerance of the photosynthetic apparatus (PSA) to irradiances up to 150 µmol PAR·m-2·s-1. Irradiance tolerance correlated with the rate of "apparent NPQ" induction. Considering that the induction of apparent NPQ involves processes significantly faster than ΔT, we suggest that the photoprotective mechanism induction rate is crucial for tolerance of the PSA to moderate irradiance during the initial stage of light acclimation (first several minutes upon the onset of illumination).

Tolerance of the Photosynthetic Apparatus to Acidification of the Growth Medium as a Possible Determinant of CO2-Tolerance of the Symbiotic Microalga Desmodesmus sp. IPPAS-2014.

The symbiotic unicellular chlorophyte Desmodesmus sp. IPPAS-2014 capable of growth at extremely high CO2 levels prohibitive for most other microalgae is an interesting model for studies of CO2 tolerance mechanisms and a promising organism for CO2 biocapture. We studied the initial (0-60 min) phase of acclimation of this microalga to an abrupt decrease in pH of the medium sparged with air/20% CO2 mixture. Acclimation of the culture to these conditions was accompanied by a sharp decrease in photochemical activity of the chloroplast followed by its recovery with a characteristic time of 10-50 min. We hypothesize that acidification of the cultivation medium by dissolving CO2 plays a key role in the observed decrease in the photochemical activity. The possible role of photosynthetic apparatus tolerance to abrupt acidification in overall high tolerance of symbiotic microalgae to extremely high CO2 levels is discussed.

Induction of Secondary Carotenogenesis in New Halophile Microalgae from the Genus Dunaliella (Chlorophyceae).

We report on the effects of high light irradiance (480 µmol quanta/(m(2)·s)) and salinity (160 and 200 g/liter NaCl) on culture growth as well as on cell lipid pigment and fatty acid (FA) composition in three novel strains of halophile microalga from the genus Dunaliella. Based on the ITS1-5.8S rRNA-ITS2 sequence and on the capability of accumulation of secondary (uncoupled from the photosynthetic apparatus) ß-carotene, the strains Dunaliella sp. BS1 and BS2 were identified as D. salina and Dunaliella sp. R5 as D. viridis. Under conditions optimal for growth, chlorophylls and primary carotenoids (mainly lutein) dominated the pigment profile of all investigated strains. The main FA were represented by unsaturated C18 FA typical of thylakoid membrane structural lipids. In all studied cells, stressors caused a decline in chlorophylls and an increase in unsaturated C16 and C18 FA associated with reserve lipids. The carotenogenic species D. salina demonstrated 10-fold increase in carotenoids accompanied by a decline in lutein and a drastic increase in ß-carotene (up to 75% of total carotenoids). In D. viridis, only 1.5-fold increase in carotenoid content took place, the ratio of major carotenoids remaining essentially unchanged. The role of the carotenogenic response in mechanisms of protection against photooxidative damage is discussed in view of halophile microalgae stress tolerance and application of the new Dunaliella strains for biotechnological production of ß-carotene.