Sep 29, 2018 3 mins read

Possibilities in Improving Bioethanol Production from Microalgae

The demand for renewable energy has dramatically increased with the population outburst and need for motorized transportation. Microalgal biomass is a source of green fuel that is gaining momentum; it is also known as the third generation of biofuel. Microalgae are great alternatives to other renewable energy because of their capability to convert unusable energy in the environment to useful fuel in large fuel concentration to biomass ratio. In addition, compared to other biofuel sources such as corn, algae has simpler needs for nutrients and conditions to grow, which are desirable characteristics to cut down energy and cost production.

Bioethanol and Microalgae

Microalgae has a high concentration of cellulose and starch which can be fermented to bioethanol. One of the bioethanol production techniques is to convert the starch and cellulose in the algae to fermentable sugars, and then use an ethanol producer (such as yeasts) to convert sugars to bioethanol. Another technique that is being studied is to genetically engineer a microalgae to directly produce bioethanol. Green Joules is extensively studying the first technology–fermenting starch to ethanol. Our team is currently studying the microalgae strain Cholera vulgaris due to its high concentration of lipids and resistance to stress (to name a few of its benefits). The biomass is collected by flocculation and centrifugation. Prior to fermentation, we have to perform saccharification, which is the hydrolysis of starch to simple sugars using acid or enzymes. Next, the sugars are fermented to ethanol by yeasts. Finally, the ethanol is purified by distillation to remove water and other impurities and is condensed into liquid form. At this stage, the ethanol can be used directly as fuel or be mixed with fossil fuel.

Challenges with Bioethanol Production

Bioethanol is not a popular choice among industries because certain production steps can become costly. For example, the fermentation process requires an anaerobic environment that needs to be established and maintained. On top of that, distillation of ethanol is an energy-intensive step, which also increases the cost of production. Our team is working on designing a technology to reduce these costs in order to make biofuels more attractive as an alternative energy source.

Opportunities for Improvement

In the process described, there are pockets of opportunities to optimize the process to offset the production cost. The fermentation process produces a solid residue at the end, which can be used as cattle-feed. On top of that, if a yeast strain used is able to do both saccharification and fermentation, there will be no need to spend money on acid or enzymes to hydrolyze starch. As such, the algal biomass that were centrifuged can be placed in a dark anaerobic aqua environment to decay and initiate fermentation. Researchers at Pennsylvania State University studied the simultaneous process of saccharification and fermentation of potato waste by using co-cultures of two strains of yeasts: Aspergillus niger and Saccharomyces cerevisiae. The effectivity of the process is affected by the concentrations of carbohydrate source (in our case, the starch), available iron, and simple sugars (such as malt extract). The cost to create bioethanol from algal biomass is currently high, but the process is largely under-studied currently. Our team is excited to explore different techniques to optimize the process of fermentation to offset the cost of production!

References:

https://www.sciencedirect.com/science/article/pii/S0016236116307724


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Alina is a second year student specializing in Microbiology and Immunology. After learning more about microbes, she became interested in...