Introduction Biofuel production from renewable resource has been extensively paid attention as a sustainable alternative for fossil fuel. As the feed of third-generation Biofuels, microalgae can produce variety of lipids, proteins, and carbohydrates in large quantities and in a relatively short time. Regarding the compatibility of these microorganisms with culture diffrent conditions and independence from the seasons of the year, the rapid growth rate, absorbing carbon dioxide and improving air quality, renewablity, non-competing with food supplies, the existence of large quantities of lipid and carbohydrate inside their cells, and abillity of Biofuels production, microalgae are known as one of the most suitable options for the Biofuels production. Biofuel production from microalgae consists of several stages, including cultivation, harvesting, drying, cell disruption, extraction (lipids or carbohydrates), and the production of Biofuels. Conclusion In the present study, by reviewing each stage of the Biofuels production from microalgae, its importance and application for bioenergy production is discussed. Algal Biofuel is not yet competitive with fossil fuels due to its high costs. Researchers are trying to produce economic algal Biofuel by improving the growth of microalgae and enriching their reserves of oil and carbohydrates, creating genetic changes, improving the design of photobioreactros, developing harvesting and drying methods, improving methods of extracting lipid and carbohydrate, and producing valuable products.

Glucose oxidase (b-D-glucose: oxygen 1-oxidoreductase; EC 1.1.3.4) is a flavoprotein which catalyzes the oxidation of b -D-glucose to D-glucono-d-lactone and H2O2 using molecular oxygen as an electron acceptor. Glucose oxidase (GOx) has important applications in several different industries. One of its new applications is in Biofuel cell (BFC) industry. Biofuel cell is a bio-electronic device which convert biochemical energy into electrical energy using a biocatalyst. Enzymatic Biofuel cell uses enzymes, for example glucose oxidase as a biocatalyst to produce electrical energy. In this study, we report the fabrication and characterization of a carbone nanotube (CNT)-based sugar/oxygen BFC operating in phosphate buffer. GOx as anodic bioelement, was immobilized on carbon fiber electrode modified with CNT and nafion. For this purpose, first, 2 mg/ml GOx enzyme solution was prepared in 200 ml potassium phosphate buffer pH=7.4. Second 100 ml of MWCNT solution was mixed with 100 ml glucose oxidase enzyme and was dropped on carbon fiber. Then 100 ml nafion was added as a thin layer on the electrode. The GOx/CNT-based bioanode and one air-cathode were combined into a functional BFC and the function of BFC was carefully investigated. After 150 min of injection of glucose solution in cell, the current was 700 mA at 490 mV. Results of fabricated cell show that presented enzymatic BFC can be used as a power source to generate electricity for implantable and portable miniature devices.

Increased energy consumption leads to a reduction in limited nonrenewable resources called fossil fuels. Due to this fact, researchers look for alternative energy sources to satisfy the need of the current generation without compromising the ability of future generations to meet their needs. As a result, nowadays the production of energy from biological sources is highly applicable and takes advantage of fossil fuel due to the limited impact on the environment. On the other hand, food cost, land use for some other purposes, and carbon emissions have risen due to the increased production of first-generation bioethanol. Even though the second-generation bioethanol from lignocellulose agricultural waste solved this problem, it again faced difficulties-to-overcome technological barriers. This, in turn, pushed researchers to come up with another alternative called the third-generation Biofuel production. The renewed promise is held in microalgae biomass as an alternative feedstock. This review deals with the important aspects of Biofuel production from algae as a renewable resource. The production processes and their merits and demerits of algae capacity in producing Biofuel are also discussed.