Faiz Ahmad Ansari

Lipid extracted algae as a source for protein and reduced sugar: a step closer to the biorefinery

The objective of this study was to investigate the feasibility of using lipid extracted algae (LEA) as a source for protein and reduced sugar, and the effects of various procedural treatments on their yields. LEA provided comparable yields of protein and reduced sugars to those from total algae. Oven drying provided highest yields of all products followed by freeze drying, while sun drying significantly lowered their yields. Effective cell disruption by microwave and autoclave increased the lipid yields from algae, but resulted in increased loss of other compounds with lipid extracting solvents lowering their yields during sequential extraction. Relatively inefficient cell disruption by ultrasonication and osmotic shock lowered the amount of cell protein lost to the lipid extracting solvents. These results highlight the complexity of concurrent extraction of all value added products from algae, and the need for proper selection of the processes to achieve the objectives of integrated biorefinery.

Adaptability of growth and nutrient uptake potential of Chlorella sorokiniana with variable nutrient loading

Chlorella sorokiniana can sustain growth in conditions hostile to other species, and possesses good nutrient removal and lipid accumulation potentials. However, the effects of variable nutrient levels (N and P) in wastewaters on growth, productivity, and nutrient uptake by C. sorokiniana have not been studied in detail. This study demonstrates the ability of this alga to sustain uniform growth and productivity, while regulating the relative nutrient uptake in accordance to their availability in the bulk medium. These results highlight the potential of C. sorokiniana as a suitable candidate for fulfilling the coupled objectives of nutrient removal and biomass production for bio-fuel with wastewaters having great variability in nutrient levels.

Evaluation of various solvent systems for lipid extraction from wet microalgal biomass and its effects on primary metabolites of lipid-extracted biomass

AbstractMicroalgae have tremendous potential to grow rapidly, synthesize, and accumulate lipids, proteins, and carbohydrates. The effects of solvent extraction of lipids on other metabolites such as proteins and carbohydrates in lipid-extracted algal (LEA) biomass are crucial aspects of algal biorefinery approach. An effective and economically feasible algae-based oil industry will depend on the selection of suitable solvent/s for lipid extraction, which has minimal effect on metabolites in lipid-extracted algae. In current study, six solvent systems were employed to extract lipids from dry and wet biomass of Scenedesmus obliquus. To explore the biorefinery concept, dichloromethane/methanol (2:1 v/v) was a suitable solvent for dry biomass; it gave 18.75% lipids (dry cell weight) in whole algal biomass, 32.79% proteins, and 24.73% carbohydrates in LEA biomass. In the case of wet biomass, in order to exploit all three metabolites, isopropanol/hexane (2:1 v/v) is an appropriate solvent system which gave 7.8% lipids (dry cell weight) in whole algal biomass, 20.97% proteins, and 22.87% carbohydrates in LEA biomass. Graphical abstract:Lipid extraction from wet microalgal biomass and biorefianry approach

Phycoremediation of Emerging Contaminants

A special group of contaminants which poses serious threat to the human health as well as the environment, but has not been fully discovered and understood, are termed as emerging contaminants (ECs). Most of such contaminants possess diverse chemical properties and are of anthropogenic origin. The ubiquitous occurrence of ECs in the environment poses serious threat to the human health as well as deleterious effects to the flora and fauna even at minute concentrations, as most of the conventional wastewater treatment plants are not designed for the effective treatment and removal of such contaminants. Therefore, other than accidental release, ECs are majorly attributed to the environment through inadequately treated wastewater, sewage, and industrial effluents. Previous studies have shown that bioremediation could be an effective tool for the treatment; however, phycoremediation of emerging contaminants have been least studied. In this chapter we have explored the possibilities of phycoremediation of ECs and have reviewed and summarized findings of most of the recent studies. This chapter exclusively covers the phycoremediation potential of various algal species for the removal of pharmaceuticals, personal care products, pesticides, endocrine disruptors, and various other organics which are considered as potential contaminants of emerging concern.

Phycoremediation: An Eco-friendly Algal Technology for Bioremediation and Bioenergy Production

Substantial amount of the refractory organics; inorganic nutrients, mainly nitrogen and phosphorus; heavy metals; etc. is discharged in conventional wastewater treatments. The concentration of such contaminants in the discharged wastewater depends on the performance and maintenance of the wastewater treatment plants (WWTPs). Though further reduction in such contaminants is possible with an aid of some of the advance technologies and skilled manpower, it makes wastewater treatment more expensive. More importantly, the running and maintenance of WWTPs are uncommon in economically weaker countries especially in the rural areas. This leads to the hunt of economically viable and environmentally sustainable alternative wastewater treatments. The truism nowadays is to recognize the emergence of phycoremediation as an alternative. Algae-based bioremediation has been found excellent for the nutrient, organic, pathogen, heavy metal, etc. removal from various types of wastewater. Green microalgae possess the unique potential of high photosynthetic activity compared to food crops and terrestrial plants. Therefore, such systems are capable of high biomass production through CO2 sequestration from the air and nutrient and organic sequestration from water. The microalgal cells contain comparatively high lipid contents; thus, algal biomass serves as an excellent feedstock for biofuels. Therefore, the choice of algal species possessing excellent phytoremediation potential as well as capable of producing high biomass is important to consider while designing the phycoremediation-based treatment systems. In this chapter, a concise partial overview of the potential and uniqueness of phycoremediation in treating various types of water and production of algal biomass for biofuels has been discussed. The environmental sustainability and economic viability aspects of phycoremediation, factors influencing the wastewater treatment, and the limitations of such technologies are covered briefly.

Harvesting of Microalgae for Biofuels: Comprehensive Performance Evaluation of Natural, Inorganic, and Synthetic Flocculants

Microalgal biomass is considered as one of the most suitable alternative feedstocks for the renewable biofuels. Microalgae have several advantages such as ability to grow in harsh environment, comparatively very high productivity, and high lipid contents. Due to such potentials, microalgal biomass is preferred over the convention biofuel feedstocks. The concentration of microalgal biomass typically ranged between 0.5 and 1 kg/m3 in the raceways or open pond type cultivation systems and around 5–10 kg/m3 in the closed photobioreactor-type cultivation systems. The bottleneck of the algal biofuels is the harvesting of microalgae biomass from diluted culture media. Irrespective of the density of the algal biomass, the water content in microalgal culture exceeds 99% that makes the separation process lengthy and energy intensive. This largely determines the economic viability of microalgae-based biofuels and by-products. Among various techniques used for the harvesting of microalgal biomass, coagulation and flocculation have been found very effective and inexpensive; however, the choice of the coagulant depends on the use of harvested biomass for desired end products. The success of microalgae harvesting by flocculation requires thorough understanding about the nature of the flocculants, its molecular weight, mode of interaction, etc., along with the understanding about the algae species to be harvested. Harvesting of microalgae by coagulation and flocculation has its own advantages and disadvantages; however, being simple and cost-effective, it is one of most preferred techniques especially if the biomass is used for biofuels.

A comparative study on biochemical methane potential of algal substrates: Implications of biomass pre-treatment and product extraction

Dried powdered algae (SDPA), heat treated algae (MHTA), lipid extracted algae (LEA) and protein extracted algae (PEA) were digested to determine biomethane potential. The average CH4 production rate was ∼2.5-times higher for protein and lipid extracted algae than for whole algae (SDPA and MHTA) whilst the cumulative CH4 production was higher for pre-treated algae. Highest cumulative CH4 production (318.7mlCH4g-1VS) was observed for MHTA followed by SDPA (307.4mlCH4g-1VS). CH4/CO2 ratios of 1.5 and 0.7 were observed for MHTA and LEA respectively. Pre-treatment processes disrupted the algal cell wall, exposing intracellular material which remained intact as opposed to product extraction processes which broke down the intracellular compounds resulting in changes in elemental composition and decreases the cumulative gas yield and CH4/CO2 ratio. Comparative analysis determined that the most profitable route of biomass utilisation was protein extraction followed by biogas production giving ∼2.5-times higher return on investment.

Microalgae for Biofuels: Applications, Process Constraints and Future Needs

Microalgae are eukaryotic (e.g. green algae, diatoms) photosynthetic organisms capable of utilizing carbon dioxide and light for the synthesis of carbohydrates as energy compounds. They have been known since many years, but their large-scale cultivation has started a few decades ago. They have the potential to grow in open systems such as raceway ponds, circular ponds and lakes and also in controlled condition like closed photobioreactors. Microalgae are advantageous considering their higher productivity than terrestrial oilseed plants and ease of cultivation in wastewater and saline water. Microalgae do not compete with agricultural land for cultivation. They have dual role such as utilization of CO2 from atmosphere as well as remediation of wastewater by utilizing nutrients from wastewater to grow into biomass. Microalgae contain different types of major metabolites and high-value products such as proteins, lipids, carbohydrates, vitamins, pigments, antioxidants, minerals, etc. (Gupta et al. 2016; Mata et al. 2010; Rawat et al. 2011; Shriwastav et al. 2014; Francavilla et al. 2015). Their major metabolites are rich in essential amino acids and essential fatty acids, e.g. omega-3 fatty acids. Productivity of these major metabolites can be increased through mode of cultivation and nutrient limitation/stresses. Commonly, the lipids from microalgae are converted into biodiesel by the process of transesterification. After lipid extraction, a huge amount of residual biomass is left that is known as lipid-extracted algae (LEA). LEA still contains the high-value metabolites like proteins and carbohydrates in residual biomass (Ansari et al. 2015; Ju et al. 2012). Lipid-extracted algae can also serve as a good resource for biomethane, bioethanol and syngas production. In addition, protein fraction of LEA has promising potential as food and feed additive for animal and aquaculture. LEA biomass due to rich nitrogen content can also be employed as a fertilizer. Therefore, considering the rich chemical composition of microalgae, it can be considered as a good feedstock for the biorefinery.

Extraction and Conversion of Microalgal Lipids

Efficient downstream processing is crucial for successful microalgal biodiesel production. Extraction of lipids and conversion of lipids are the main downstream steps in microalgal biodiesel production process. This chapter provides the overview of the conventional as well as novel extraction and conversion technologies for microalgal lipids. The extraction and conversion technologies have to be environmentally friendly and energy efficient for sustainable and economically viable microalgal biodiesel production.