(Madeira et al. 2017; D'Este et al. 2017). A wide range of pigment molecules like
carotenoids, astaxanthin which are antioxidants are produced by microalgae
(Rammuni et al. 2019), polyunsaturated fatty acids (PUFAs), antimicrobial and
anti-carcinogenic compounds (Kumar et al. 2019; Marrez et al. 2019), storage lipids
or triacylglycerides (Xin et al. 2019), proteins, carbohydrates, and amino acids
(Rizwan et al. 2018). Microalgae have garnered recent research attention particularly
for bio-refinery (i.e., sustainable generation of biofuels along with high value
metabolic co-products products by consolidated bio processing). In this context,
oleaginous microalgae like Nannochloropsis, Schizochytrium, and Botryococcus
(with oil content ranging from 20% to 60%, and up to 80%) have been widely
explored for the biodiesel production (Bardhan et al. 2019) and other liquid biofuels
(de Morais et al. 2019) (Table 7.1).
Genetic engineering tools have been used to modify microalgae for recombinant
protein production, express genes to synthesize novel products, and increase the
yield of natural value added products (Gangl et al. 2015). For example,
Chlamydomonas reinhardtii was genetically engineered to produce xylitol (finds
application in the food and confectionary industry as artificial sweetener) by
integrating a xylose reductase gene from Neurospora crassa into its chloroplast
genome (Pourmir et al. 2013). Furthermore, recombinant microalgae are promising
cell factories for therapeutic protein production including antibodies, vaccines, and
hormones (Gong et al. 2011). Recently, Schizochytrium sp. was genetically modified
to produce a new antiviral vaccine against zika virus (Márquez-Escobar et al. 2018).
7.2.2 Microalgae from the Environmental Microbiology
Perspective (Fig. 7.2)
Discharge of industrial effluent, municipal solid waste, agro-industrial waste water,
pharmaceutical contaminants into freshwater systems has led to serious health issues
and associated environmental hazards. In this context, microalgae mediated wastewater treatment and bioremediation of polluted contaminants has garnered recent
research attention as it is solar-power driven, economically comprehensive, and
sustainable strategy to mitigate these issues (Xiong et al. 2018). de Souza Leite et
al. (2019) reported more than 90% removal of organic matter (in municipal and
piggery wastewater) using Chlorella sorokiniana. Another study demonstrated the
potential of using microalgae–bacteria consortium (two microalgal species, viz.
Desmodesmus spp. and Scenedesmus obliquus) for the treatment of leachate/wastewater mixture along with microalgal biomass production having enhanced amount
of accumulated lipids for the production of biodiesel (Hernández-García et al. 2019).
In addition to wastewater treatment, microalgae find immense application in soil
as bio-fertilizers for nitrogen recovery (de Souza et al. 2019). Khan et al. 2019
demonstrated bio-refinery approach by integrating the phycoremediation potential of
Chlorella minutissima with the subsequent production of biodiesel and organic
manure. In terms of CO 2 capture process, microalgae has been found to have better
(10–50 times more) CO 2 fixation ability than plants (Yadav and Sen 2017).
7 Aquatic Microbial Oxygenic Phototrophs: A Short Treatise on Diverse. . .
139
carotenoids, astaxanthin which are antioxidants are produced by microalgae
(Rammuni et al. 2019), polyunsaturated fatty acids (PUFAs), antimicrobial and
anti-carcinogenic compounds (Kumar et al. 2019; Marrez et al. 2019), storage lipids
or triacylglycerides (Xin et al. 2019), proteins, carbohydrates, and amino acids
(Rizwan et al. 2018). Microalgae have garnered recent research attention particularly
for bio-refinery (i.e., sustainable generation of biofuels along with high value
metabolic co-products products by consolidated bio processing). In this context,
oleaginous microalgae like Nannochloropsis, Schizochytrium, and Botryococcus
(with oil content ranging from 20% to 60%, and up to 80%) have been widely
explored for the biodiesel production (Bardhan et al. 2019) and other liquid biofuels
(de Morais et al. 2019) (Table 7.1).
Genetic engineering tools have been used to modify microalgae for recombinant
protein production, express genes to synthesize novel products, and increase the
yield of natural value added products (Gangl et al. 2015). For example,
Chlamydomonas reinhardtii was genetically engineered to produce xylitol (finds
application in the food and confectionary industry as artificial sweetener) by
integrating a xylose reductase gene from Neurospora crassa into its chloroplast
genome (Pourmir et al. 2013). Furthermore, recombinant microalgae are promising
cell factories for therapeutic protein production including antibodies, vaccines, and
hormones (Gong et al. 2011). Recently, Schizochytrium sp. was genetically modified
to produce a new antiviral vaccine against zika virus (Márquez-Escobar et al. 2018).
7.2.2 Microalgae from the Environmental Microbiology
Perspective (Fig. 7.2)
Discharge of industrial effluent, municipal solid waste, agro-industrial waste water,
pharmaceutical contaminants into freshwater systems has led to serious health issues
and associated environmental hazards. In this context, microalgae mediated wastewater treatment and bioremediation of polluted contaminants has garnered recent
research attention as it is solar-power driven, economically comprehensive, and
sustainable strategy to mitigate these issues (Xiong et al. 2018). de Souza Leite et
al. (2019) reported more than 90% removal of organic matter (in municipal and
piggery wastewater) using Chlorella sorokiniana. Another study demonstrated the
potential of using microalgae–bacteria consortium (two microalgal species, viz.
Desmodesmus spp. and Scenedesmus obliquus) for the treatment of leachate/wastewater mixture along with microalgal biomass production having enhanced amount
of accumulated lipids for the production of biodiesel (Hernández-García et al. 2019).
In addition to wastewater treatment, microalgae find immense application in soil
as bio-fertilizers for nitrogen recovery (de Souza et al. 2019). Khan et al. 2019
demonstrated bio-refinery approach by integrating the phycoremediation potential of
Chlorella minutissima with the subsequent production of biodiesel and organic
manure. In terms of CO 2 capture process, microalgae has been found to have better
(10–50 times more) CO 2 fixation ability than plants (Yadav and Sen 2017).
7 Aquatic Microbial Oxygenic Phototrophs: A Short Treatise on Diverse. . .
139