•Spirulina biorefinery contribute to greenhouse gases fixation and effluent treatment.•More than 30% of the world biomass production is from genus Spirulina.•Biorefineries are the best alternative ...for the economic performance of Spirulina.
Microalgae biorefinery systems have been extensively studied from the perspective of resources, energy expenditure, biofuel production potential, and high-added value products. The genus Spirulina (Arthrospira) stands out among the microalgae of commercial importance. It accounts for over 30% of biomass produced globally because of high protein concentration and, carotenoid and phycocyanin content. Spirulina cultivation can be used to reduce greenhouse gases and for effluent treatment. Furthermore, its cellular morphology facilitates biomass recovery, which contributes to the process cost reduction. Spirulina biomass is widely applicable in food, feed, cosmetics, biofertilizers, biofuels, and biomaterials. A feasibility analysis of Spirulina biorefinery would provide specific information for the decision-making for the improvement of the Spirulina production process. In that context, this review aimed to present a parameter assessment to contribute to the economic viability of Spirulina production in a biorefinery system.
Renewable energy sources e.g. biofuels, are the focus of this century. Economically and environmental friendly production of such energies are the challenges that limit their usages. Microalgae is ...one of the most promising renewable feedstocks. However, economical production of microalgae lipid in large scales is conditioned by increasing the lipid content of potential strains without losing their growth rate or by enhancing both simultaneously. Major effort and advances in this area can be made through the environmental stresses. However, such stresses not only affect the lipid content and species growth (biomass productivity) but also lipid composition. This study provides a comprehensive review on lipid enhancement strategies through environmental stresses and the synergistic or antagonistic effects of those parameters on biomass productivity and the lipid composition. This study contains two main parts. In the first part, the cellular structure, taxonomic groups, lipid accumulation and lipid compositions of the most potential species for lipid production are investigated. In the second part, the effects of nitrogen deprivation, phosphorus deprivation, salinity stress, carbon source, metal ions, pH, temperature as the most important and applicable environmental parameters on lipid content, biomass productivity/growth rate and lipid composition are investigated.
•Cellular structure and taxonomy of potential microalgae for biofuel production were considered.•The quality of lipid accumulation and lipid compositions of those strains were investigated.•The effect of environmental stressors on lipid enhancement in those strains was investigated.•The effect of stressors on biomass productivity and lipid composition was investigated.
Due to the high consumption rate of fermented milk products such as yogurt, the fortification of these products will effectively reduce diseases associated with nutritional deficiencies. In the ...present study, after incorporating Spirulina into yogurt at four different concentrations (0.25, 0.5, 0.75 and 1%), we studied its effect on the fermentation process, texture, nutraceutical and sensory characteristics of yogurt. The addition of 0.25% of Spirulina was significantly sufficient to accelerate the end of fermentation (p < 0.05) and conserve the textural properties and sensory acceptability of the final milk product. This treatment also exhibited significant better water holding capacity and lower whey syneresis during 28 days of storage. During this period, the colored yogurt showed negligible variations for the L*, a* and b* indices, reflecting the strong stability of Spirulina color. Thanks to its high content in pigments, Spirulina considerably improve the antioxidant activity of the new formulated yogurt. Overall, it can be concluded that Spirulina can be used as a natural ingredient to develop a novel yogurt with high nutritional properties.
•Yogurt with Spirulina had a higher protein, fat and dietary fiber contents.•Yogurt supplemented with 0.25% of Spirulina gave closer results to control sample for textural and sensory evaluation.•This treatment also exhibited significant better water holding capacity and lower whey syneresis during storage.•Spirulina can be used as a natural ingredient to develop a novel yogurt with high nutritional properties.
The rapid growth of human population has led to mounting energy demands, which is projected to increase by 50% or more by 2030. The natural petroleum can not catch-up the current consumption rate, ...which is already reported to be 105 times faster than nature can create. Besides, the use of fossil fuels is devastating to our environment through greenhouse gas emissions and consequent global warming. Therefore, the search for ‘clean’ energy has become the most overwhelming challenges. Currently, several alternatives are being studied and implemented. Biofuels, fuels from living organisms, provide environmental benefits, since their use leads to a decrease in the harmful emissions of CO2 and hydrocarbons and, to the elimination of SOx emissions, with a consequent decrease in the greenhouse effects. Unfortunately, the present biofuel projections are based on feed-stocks that are also food commodities and resources suitable for conventional agriculture. One possibility to overcome the problem is the cultivation of micro-algae and switching to third generation biofuels, which seem to be a promising source since algae are able to efficiently convert sunlight, water, and CO2 into a variety of products suitable for renewable energy applications. Therefore, this review is intended to recapitulate current works on micro-algal biofuel production potential and discuss possible ways to put it into practice. This review starts by highlighting the advantages and various forms of micro-algal biofuels. Some of the micro-algal species proved to be suitable for biofuel production so far are considered, with particular emphasis on Scenedesmus obliquus. The recent attempts and achievements in improving the economies of production through genetic and metabolic engineering of micro-algal strains are also addressed. Other potential applications such as wastewater treatment and CO2 mitigation that can be coupled with biofuel production are described. Finally, the promises and challenges of algae to biofuel industry are uncovered.
Biological CO2 fixation and wastewater treatment by using microalgae has recently received growing interest. Microalgae can be cultivated in photobioreactors by utilizing CO2 from point sources such ...as power plants, cement manufacturing facilities and waste water from industrial, municipal, dairy facilities. These processes can provide the nutrient sources for sunlight microalgae photosynthesis. Thus, microalgae culture can contribute simultaneously to both CO2 fixation and wastewater treatment. This article presents a critical review, focusing on various photobioreactors and microalgae species cultures in wastewater that can capture high amounts of CO2 and provide high quality biofuel. In this respect, a number of relevant topics are discussed in this review: a) current wastewater treatment processes, b) wastewater treatment using microalgae, c) classification of photobioreactors, d) microalgae growth parameters and d) the CO2 capture mechanism.
It is increasing clear that biofuels can be a viable source of renewable energy in contrast to the finite nature, geopolitical instability, and deleterious global effects of fossil fuel energy. ...Collectively, biofuels include any energy-enriched chemicals generated directly through the biological processes or derived from the chemical conversion from biomass of prior living organisms. Predominantly, biofuels are produced from photosynthetic organisms such as photosynthetic bacteria, micro- and macro-algae and vascular land plants. The primary products of biofuel may be in a gas, liquid, or solid form. These products can be further converted by biochemical, physical, and thermochemical methods. Biofuels can be classified into two categories: primary and secondary biofuels. The primary biofuels are directly produced from burning woody or cellulosic plant material and dry animal waste. The secondary biofuels can be classified into three generations that are each indirectly generated from plant and animal material. The first generation of biofuels is ethanol derived from food crops rich in starch or biodiesel taken from waste animal fats such as cooking grease. The second generation is bioethanol derived from non-food cellulosic biomass and biodiesel taken from oil-rich plant seed such as soybean or jatropha. The third generation is the biofuels generated from cyanobacterial, microalgae and other microbes, which is the most promising approach to meet the global energy demands. In this review, we present the recent progresses including challenges and opportunities in microbial biofuels production as well as the potential applications of microalgae as a platform of biomass production. Future research endeavors in biofuel production should be placed on the search of novel biofuel production species, optimization and improvement of culture conditions, genetic engineering of biofuel-producing species, complete understanding of the biofuel production mechanisms, and effective techniques for mass cultivation of microorganisms.
•Challenges and opportunities of biofuels in addressing global energy demands were investigated.•Third generation biofuels using microalgae seems to be promising energy sources in the long run.•Improving microalgae species and achieving more in-depth understanding of biofuel production mechanisms is essential.
Microalgae are a potential source of sustainable biomass feedstock for biofuel generation, and can proliferate under versatile environmental conditions. Mass cultivation of microalgae is the most ...overpriced and technically challenging step in microalgal biofuel generation. Wastewater is an available source of the water plus nutrients necessary for algae cultivation. Microalgae provide a cost-effective and sustainable means of advanced (waste)water treatment with the simultaneous production of commercially valuable products. Microalgae show higher efficiency in nutrient removal than other microorganisms because the nutrients (ammonia, nitrate, phosphate, urea and trace elements) present in various wastewaters are essential for microalgal growth. Potential progress in the area of microalgal cultivation coupled with wastewater treatment in open and closed systems has led to an improvement in algal biomass production. However, significant efforts are still required for the development and optimization of a coupled system to simultaneously generate biomass and treat wastewater. In this review, the systematic description of the technologies required for the successful integration of wastewater treatment and cultivation of microalgae for biomass production toward biofuel generation was discussed. It deeply reviews the microalgae-mediated treatment of different wastewaters (including municipal, piggery/swine, industrial, and anaerobic wastewater), and highlight the wastewater characteristics suitable for microalgae cultivation. Various pretreatment methods (such as filtration, autoclaving, UV application, and dilution) needed for wastewater prior to its use for microalgae cultivation have been discussed. The selection of potential microalgae species that can grow in wastewater and generate a large amount of biomass has been considered. Discussion on microalgal cultivation systems (including raceways, photobioreactors, turf scrubbers, and hybrid systems) that use wastewater, evaluating the capital expenditures (CAPEX) and operational expenditures (OPEX) of each system was reported. In view of the limitations of recent studies, the future directions for integrated wastewater treatment and microalgae biomass production for industrial applications were suggested.
•Challenges in using wastewater for microalgae cultivation and biomass production.•Treatment of different wastewaters and reuse of the treated water.•Recovery of valuable nutrients (N/P) and removal of organic pollutants.•Application of wastewater in raceways, photobioreactors, turf scrubbers, and hybrid systems.•Genetically engineered microalgae for efficient wastewater treatment.
Biological pretreatment (BP) is a promising approach for treating microalgae and lignocellulosic biomass (LCB) during biofuels production that uses mostly fungal and bacterial strains or their ...enzymes. Pretreatment with fungi requires long incubation time (weeks to months), whereas, bacterial and enzymatic pretreatments can be completed by only a few hours to days. Nevertheless, fungal pretreatment especially with white-rot fungi (WRF) is predominantly used in BP of biomass for its high efficiency and downstream yields. According to the recent reports, delignification of LCB by WRF may vary between 3% and 72% with a maximum 120% increase in the biofuel yield. Compared to the untreated microalgae biomass, the downstream yields of the respective biofuels were found to be increased by 22–159% after bacterial pretreatment, while enzymatic pretreatment improved as much as 485% of the final yield. Despite the results are promising, exploitation of BP on large scale is still bottlenecked by some technoeconomic hurdles, which need to be overcome through further fundamental and applied researches. This paper presents a comprehensive and in-depth review on BP for LCB and microalgae biomass by focusing on the relevant overviews and perspectives, technological approaches, mechanisms, influencing factors, and recent research progresses. Finally, challenges and future outlooks are discussed in the concluding sections.
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•Biological pretreatment (BP) is a sustainable approach for 2G and 3G biofuels.•BP can be done by using fungi, bacteria, enzymes, ensiling and microbial consortium.•Microbes produce ligninolytic and hydrolytic enzymes to work on biomass during BP.•A good number of factors affect the efficiency of BP that need to be optimized.•Long pretreatment time is a major drawback for BP in its exploitation on large scale.
The potential of microalgae as an alternative energy source has been adequately studied. However, exclusive use of microalgae as an energy feedstocks cannot warrant their scalability and economical ...sustainability due to the high cost involved in their biomass processing. The co-processing of microalgae biomass with other related bio-refinery applications can offset their cost and improve their sustainability. Thus, it triggers up the need of exploring the potential of microalgae biomass beyond their typical use. Microalgae offer interesting features to qualify them as alternative feedstocks for various bio-refinery applications. Microalgae have unique abilities to utilize them for industrial and environmental applications. Thus, this review discusses to expand the scope of integrating microalgae with other biotechnological applications to enhance their sustainability. The use of microalgae as a feed for animal and aquaculture, fertilizers, medicine, cosmetic, environmental and other biotechnological applications is thoroughly reviewed. It also highlights the barriers, opportunities, developments, and prospects of extending the scope of microalgae. This study concludes that sustained research funding, and a shift of microalgae focus from biofuels production to bio-refinery co-products can qualify them as promising feedstocks.
Moreover, technology integration is inevitable to off-set the cost of microalgae biomass processing. It is expected that this study would be helpful to determine the future role of microalgae in bio-refinery applications.
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