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The study aimed at understanding the biochemical and molecular level modifications in Desmodesmus sp. under lipid inducing stress conditions. The low-temperature (5 °C) incubation and nitrogen starvation reduced the PS II electron transport in microalga with a maximum reduction of 50-57% in ET 0 /ABS values. The PS II electron transport recovered in UV treated cultures after an initial reduction of 87-93% in ET 0 /ABS values. A 2.7-4.4 fold increase in ROS and MDA levels was observed under low-temperature incubation, and nitrogen starvation. The UV treatment caused 1.3-2.4 fold higher ROS and MDA levels than control. The low-temperature incubated, nitrogen starved, and UV treated cultures showed 2.4-4 fold higher acc D gene expression. A higher rbc L gene expression was observed under low-temperature stress. The study showed modifications in PS II electron transport, oxidative status, and expression of acc D and rbc L genes under stress conditions., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The indigenous freshwater microalga Desmodesmus sp. produces ALA rich lipids (about 23%). The phytohormones (DAH and KIN; 0.5 mg L -1 ) increased the biomass yield and lipid content of microalga by 1.4-1.7 fold. Mixotrophic cultivation (500 mM glucose and 100 mM sodium acetate) enhanced the biomass yield and lipid content by 1.8-2.7 fold. The sodium azide (1.0 mM) led to a 1.5 fold and 1.7 fold enhancement in the lipid content and ALA fraction of total fatty acids, respectively without affecting the biomass yield. The low temperature (5 °C) as the second stage of cultivation enhanced the ALA fraction of total fatty acids by 1.2-1.5 fold for untreated, phytohormone supplemented and mixotrophic cultures, without affecting the biomass yield. These cultivation strategies could, therefore, be used for enhancement of ALA rich lipids in microalgae without compromising the biomass production., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The indigenous microalga, Desmodesmus sp. produced alpha-linolenic acid (ALA) rich lipids in response to low temperature and UV treatment. Incubation at 5 °C showed a 1.5 fold increase in lipid content (34% w/w) with 44% ALA fraction of total fatty acids. The UV treatment (UV 60 min) exhibited a 1.4 fold increase in biomass productivity and 1.6 fold increase in lipid content (37% w/w) with ALA fraction as 31% of total fatty acids. The nitrogen stress enhanced the lipid content (39% w/w) with a reduced ALA fraction (18%) of total fatty acids. The UV treated cultures (UV 40 and 60 min) on incubation at 5 °C showed maximum lipid accumulation (59 to 62% w/w) with ALA fraction of total fatty acids as 39 to 42%. The incubation of nutrient-replete and UV treated cultures at low-temperature could therefore be used for the production of ALA-rich lipids in microalgae., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

A mixed culture of microalgae, containing two Scenedesmus species, was analysed to determine its potential in coupling of pulp and paper mill effluent treatment and microalgal cultivation. Laboratory studies suggested that 60% concentration of wastewater was optimum for microalgal cultivation. A maximum of 82% and 75% removal of BOD and COD respectively was achieved with microalgal cultivation in outdoor open pond. By the end of the cultivation period, 65% removal of NO3-N and 71.29% removal of PO4-P was observed. The fatty acid composition of mixed microalgal culture cultivated with effluent showed the palmitic acid, oleic acid, linoleic acid and α-linolenic acid as major fatty acids. The results obtained suggest that pulp and paper mill effluent could be used effectively for cultivation of microalgae to minimise the freshwater and nutrient requirements., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Scenedesmus obtusus, a freshwater microalga, was evaluated for its growth and biochemical characteristics under various culture conditions. S. obtusus was tolerant at all tested CO2 concentrations up to 20%. Among the different nitrogen sources, urea showed enhanced biomass productivities up to 2-fold compared to control, where the nitrogen source was sodium nitrate. Light intensity and photoperiod had a significant effect on growth rate and biomass productivity. The growth rate was observed maximum under continuous light exposure at the light intensities, 30μmolm(-2)sec(-1) and 60μmolm(-2)sec(-1) The species was able to tolerate the salinity levels up to 25mM NaCl, where, the increase in the concentration of NaCl suppressed the growth. Ammonium acetate and glycine showed better growth rate and biomass productivity indicating mixotrophic ability of S. obtusus. Supplementation of acetate and bicarbonate significantly enhanced the biomass productivity. Biodiesel properties of S. obtusus cultivated at various culture conditions were estimated., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

The present study analyzes the effect of thermal pretreatment for enhancing the biomethane potential of defatted algal biomass of Scenedesmus dimorphus through statistically guided experimental design. To this end, defatted microalgal biomass at various concentrations (1, 3 and 5 g L(-1)) was pretreated at elevated temperatures (100, 120 and 150°C) for 20, 40 and 60 min. The solubilised TOC was favourably enhanced up to 71 mg L(-1) after pretreatment at a temperature of 150°C for reaction time of 60 min. The methane yield was substantially enhanced (up to 60%) and could be correlated with an increase in organic matter solubilisation and enhanced biodegradability via thermal pretreatment. The optimisation of the integrated thermal pretreatment-biomethanation process resulted in up to 1.6-fold increase in methane yield., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Five indigenous microalgal strains of Scenedesmus, Chlorococcum, Coelastrum, and Ankistrodesmus genera, isolated from Indian fresh water habitats, were studied for carbon-dioxide tolerance and its effect on growth, lipid and fatty acid profile. Scenedesmus dimorphus strain showed maximum growth (1.5 g/L) and lipid content (17.83% w/w) under CO2 supplementation, hence selected for detailed evaluation. The selected strain was alkaline adapted but tolerated (i) wide range of pH (5-11); (ii) elevated salinity levels (up to 100 mM, NaCl) with low biomass yields and increased carotenoids (19.34 mg/g biomass); (iii) elevated CO2 levels up to 15% v/v with enhancement in specific growth rate (0.137 d(-1)), biomass yield (1.57 g/L), lipid content (19.6% w/w) and CO2 biofixation rate (0.174 g L(-1) d(-1)). Unsaturated fatty acid content (alpha linolenic acid) increased with CO2 supplementation in the strain., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Abstract: A comparative life cycle assessment of CO2 capture potential of microalgae, Scenedesmus dimorphus, during autotrophic cultivation in closed airlift photobioreactor and open raceway pond under Indian conditions has been carried out. The LCA inventory inputs for the both the systems were entirely based on primary experimental data obtained by algal cultivation in 1000-L pilot-scale raceway pond and 5-L airlift photobioreactor, respectively. The primary energy demand, environmental impacts and Net CO2 capture efficiency of both the systems were evaluated. The results indicated that the primary energy demand and GWP of airlift photobioreactor were 3.7-fold higher than raceway pond. The NERCO2 (defined as net emission ratio of CO2 and estimated as ratio of CO2 sequestered/CO2 emitted) of raceway pond was fourfold higher as compared to airlift photobioreactor; however, both the cultivation systems were observed to be net negative in terms of CO2 sequestration. However, the process can become net CO2 positive, with up to fourfold and 7.5-fold enhancement in biomass productivities (wrt base value) for raceway pond and airlift photobioreactor, respectively. Further, LCA predictions indicated that utilization of energy-efficient motors with lower specific energy consumptions for microalgae cultivation would facilitate algal cultivation systems to achieve net CO2-positive sequestration. [ABSTRACT FROM AUTHOR]

Dunaliella salina is a halotolerant marine microalga, known for the accumulation of β-carotene. The BCH-type β-carotene hydroxylase plays a major role in the conversion of β-carotene to xanthophylls. The β-carotene hydroxylase from the chlorophycean microalga, Chlamydomonas reinhardtii was amplified, and the sequence alignment analysis showed that the amplified gene belongs to the group of BCH-type hydroxylases. The amplified β-carotene hydroxylase gene with rubisco promoter and chloroplast transit peptide was introduced into the genome of the D. salina by Agrobacterium -mediated genetic transformation. The carotenoid analysis showed a 3-fold increase of violaxanthin at growth stage and a 2-fold increase of zeaxanthin under stress conditions in transformed D. salina . [ABSTRACT FROM AUTHOR]

Indigenous freshwater microalgae from natural habitats may have potential for bio-mitigation of atmospheric CO 2 . The present study evaluates the response of three indigenous microalgal isolates viz., Desmodesmus sp., Kirchneriella sp. and Acutodesmus sp., to CO 2 rich environment (10, 20 and 30%) in a closed photobioreactor. In a time course study, levels of CO 2 in culture medium were observed to modulate the activity of carbonic anhydrase (CA), a key enzyme of carbon concentrating mechanism (CCM) of microalgae. The CA activity decreased on availability of free CO 2 and increased on depletion of free CO 2 in the culture medium. Maintenance of algal cultures in CO 2 rich environment for a period of 16 days enhanced the biomass concentration, specific growth rate, chlorophyll and carbon dioxide biofixation rate by 2–4 fold. Overall productivity, carbon, carotenoid and lipid contents also increased. Palmitic and oleic acids were the major fatty acids of the algal lipids. CO 2 rich environment affected the fatty acid profile in Desmodesmus sp. with an increase in unsaturated fatty acids. [ABSTRACT FROM AUTHOR]

Though the potential of micro algal biotechnology for business or industry is widely acknowledged for long, the potential did not get translated much into the benefits for the society. The article discusses the approaches that can be adopted by the universities in making algal technologies reach out to the society. It argues the urgent need to review and assess on what need to be done to deliver the promise that algal biotechnology has for the society. The article identifies four major challenges to universities in making algal technology work in today's knowledge society and knowledge economy. These four challenges are bio-business and knowledge transfer, knowledge and technology integration, human resources development and capacity building, and expanding boundaries of scholarship. There is a need to evolve some innovative and new approaches for addressing these challenges. Many institutes and universities of high repute are modifying their system by introducing certain innovations to avoid compartmentalisation of knowledge or/and different systems of education. Three routes to planning careers in algal biotechnology are identified - developing specialist educationists and researchers in various branches related to algal biotechnology; careers in algal biotechnology to cater to the needs of the industry; and careers in algal biotechnology to cater to the needs of society. It is argued that developing a new 'anatomy' which can serve both basic science and business may be one of the keys for algal technologies to reach out to the society. [ABSTRACT FROM AUTHOR]

Abstract: Growth of Botryococcus braunii was studied using different autotrophic media such as bold basal medium (BBM), and bold basal with ammonium carbonate (BBMa), BG11, modified Chu 13 medium. Among the different autotrophic media used, BG11 was found to be the best medium for biomass and hydrocarbon production, although B. braunii showed appreciable level of growth and biomass production in all the tested media. The culture maintained at 16:8h light and dark cycle with 1.2±0.2klux light intensity at 25±1°C temperature was found to be the best for growth (2.0 and 2.8gL−1 of biomass was produced by the B. braunii strains SAG 30.81 and LB-572, respectively) and hydrocarbon production (46% and 33%, respectively, by SAG 30.81 and LB 572 strains on dry weight basis) whereas continuous illumination with agitation at 90rpm had maximum influence for the production of exopolysaccharides. The results of the present study indicate that the organism can acclimatize to different culture conditions and to a wide range of culture media with production of more than one metabolite. [Copyright &y& Elsevier]

The present study is focused on bioavailability and antioxidant property of carotenoids from microalgal biomass elucidated in rat model. Microalgal biomass containing 200μM equivalent of β-carotene, astaxanthin and lutein per rat from Spirulina platensis, Haematococcus pluvialis and Botryococcus braunii biomass respectively was dispersed in olive oil and administered to rats for a period of 15days. The levels of these carotenoids in the plasma, liver and eye were examined by high performance liquid chromatography and also confirmed by mass spectroscopy. The maximum peak levels (nmol/g) of β-carotene (615.61±85.54), astaxanthin (896.51±101.76) and lutein (679.55±74.08) were detected in the liver followed by the eye and plasma. Astaxanthin accumulation in rats fed with H. pluvialis group was higher when compared to S. platensis and B. braunii groups. In H. pluvialis fed group, antioxidant enzymes catalase, superoxide dismutase, peroxidase and lipid peroxidation levels were high in the plasma and liver compared to S. platensis and B. braunii fed groups. These results indicate that the astaxanthin from H. pluvialis has better bioavailability and better antioxidant properties compared to other carotenoids. [ABSTRACT FROM AUTHOR]

Abstract: The present study focused on cultivation, seasonal variation in growth, hydrocarbon production, fatty acids profiles of Botryococcus braunii (LB-572 and N-836) in raceway & circular ponds under outdoor conditions. After 18days of cultivation the biomass yield and hydrocarbon contents were increased in both raceway and circular ponds. The fat content was found to be around 24% (w/w) with palmitic and oleic acids as prominent fatty acids. Hydrocarbons of C20–C30 carbon chain length were higher in raceway and circular ponds. Maximum biomass yield (2gL−1) and hydrocarbon content (28%) were observed in Nov–Dec. In case of B. braunii (N-836) after 25days of cultivation the biomass yield was 1gL−1 and hydrocarbon content was 27%. Supplementation of 0.1% NaHCO3 in the medium resulted in biomass yield of 1.5gL−1 and hydrocarbon content of 30% compared to control. [Copyright &y& Elsevier]

Abstract: Growth of Botryococcus braunii (race ‘A’) and production of its constituents viz, hydrocarbon, carbohydrate, fatty acid, and carotenoids were influenced by different levels of salinity. Under salinity at 34mM and 85mM, 1.7–2.25-fold increase in the relative proportion of palmitic acid and two fold increase in oleic acid were observed. A twofold increase in carotenoid content was noticed at 85mM salinity with lutein (75% of total carotenoid) as the major carotenoid followed by β-carotene. The increase in biomass yields and changes in other constituents indicated the influence of salinity and the organism’s adaptability to the tested levels of salinity (17mM to 85mM). [Copyright &y& Elsevier]

Highlights: [•] Thermal pretreatment to biomass was optimised for improved biomethanation. [•] Pretreatment resulted in enhanced biodegradability of defatted algal biomass. [•] Methane yield enhanced up to 60% after pretreatment. [Copyright &y& Elsevier]