Physiological and Biochemical Responses of Bicarbonate Supplementation on Biomass and Lipid Content of Green Algae Scenedesmus sp. BHU1 Isolated From Wastewater for Renewable Biofuel Feedstock

Abstract

In the present study, different microalgae were isolated from wastewater environment and evaluated for higher growth and lipid accumulation. The growth adaptability of all the isolated microalgae were tested for carbon source with supplementation of sodium bicarbonate in BG-11 N+ medium. Further based on the uptake rate of sodium bicarbonate and growth behavior, microalgal strains were selected for biofuel feedstock. During the study, growth parameters of all the isolates were screened after supplementation with various carbon sources, in which strain Scenedesmus sp. BHU1 was found highly effective among all. The efficacy of Scenedesmus sp. BHU1 strain under different sodium bicarbonate (4–20 mM) concentration, in which higher growth 1.4 times greater than control was observed at the concentration 12 mM sodium bicarbonate. In addition, total chlorophyll content (Chl-a + Chl-b), chlorophyll fluorescence (Fv/Fm, Y(II), ETR max, and NPQmax), and biomass productivity were found to be 11.514 μg/ml, 0.673, 0.675, and 31.167 μmol electrons m−2 s−1, 1.399, 59.167 mg/L/day, respectively, at the 12 mM sodium bicarbonate. However, under optimum sodium bicarbonate supplementation, 56.920% carbohydrate and 34.693% lipid content were accumulated, which showed potential of sodium bicarbonate supplementation in renewable biofuel feedstock by using Scenedesmus sp. BHU1 strain.

Combination of bicarbonate and low temperature stress induces the biosynthesis of both arachidonic and docosahexaenoic acids in alkaliphilic microalgae Dunaliella salina HTBS

“…The addition of bicarbonate alleviated low temperature-induced photosynthesis impairment, as Fv/Fm increased by 54.67%, 34.22%, 14.67% and 12% at 0.075 M, 0.15 M, 0.3 M and 0.6 M bicarbonate, respectively, which was consistent with the previous study (Sun et al, 2020). Similarly, microalgae cells with an increased bicarbonate conditions showed a gradually significant rise in Fv/ Fm, which suggested an increase in photosynthetic carbon fixation and metabolic activity (Singh et al, 2022). With the sustained addition of bicarbonate, the salinity increases to suppress of photosynthetic activity (Salbitani et al, 2020).…”

“…The increased non-photochemical quenching (NPQ) means that the cells are suffering from environmental stress (Xue et al, 2022). Therefore, the reductions of NPQ at 0.075 M and 0.15M bicarbonate groups suggest that a certain bicarbonate content can help to relieve the stress caused by low temperature, which is consistent with the report that a high concentration of CO 2 declines NPQ to benefit carbon and nitrogen sequestration, resulting in more metabolite synthesis (Singh et al, 2022). As a consequence, the carbon and nitrogen removal rates of the combined groups were significantly increased compared to low temperature treatment without bicarbonate supply.…”

“…Similar results were also obtained for protein content analysis (19.66% to 26.03%) (Figure 1D). With the addition of bicarbonate, the increased C/N ratio results in more lipid and carbohydrate biosynthesis for carbon storage with the excess energy (Peng et al, 2019;Singh et al, 2022;Xie et al, 2022). Although the lipid accumulation and protein biosynthesis present competitive relationships with each other, the increased profile of both lipid and protein content were observed in this study, possibly owing to the modified nitrogen content (750 mg/L), which was 10-fold higher than f/ 2 medium and promotes more intracellular conversion to protein (Vishwakarma et al, 2019).…”

Mechanisms of Stress Tolerance in Cyanobacteria under Extreme Conditions

“…These environmental condition affect the morphology (cell wall alteration), biochemicals (production of screening pigments), or physiology (state transitions), or there may be some genetic changes that occur as a result of acclimatization under the environmental extremes [18]. Temperature High [30,31] Low [32][33][34] 5 Salt Salinity [35][36][37] Osmoticum [38][39][40] 6 Chemicals Pesticides [41] Heavy metals [42][43][44] 7 Desiccation [45][46][47] In addition, the imposition of stress can lead to changes in the metabolic behaviors, such as the enhanced synthesis of polyunsaturated fatty acids [48] and enhanced concentration of photosystem unit in the thylakoid membrane, which is commonly observed [49]. However, the response time of short-term reactions are usually less than a minute, and rare structural modifications have been observed [50].…”

Integrating biological and chemical CO2 sequestration using green microalgae for bioproducts generation

“…Some studies have explored the utilization of membrane carbonation and carbonation columns and sumps to increase the carbon transfer efficiency into the water (Eustance et al, 2020;Lai et al, 2020). While others, such as Pancha et al (2015), Najafabadi et al (2015) and Singh et al (2022) have studied the use of bicarbonates (HCO − 3 ) to increase biomass productivity as well as the lipids content. The strategy of feeding HCO −…”