Abstract
Due to its high carbohydrate content, algae biomass can be employed as feedstock to produce hydrogen (H2) by fermentation. However, to make the carbohydrates entrapped within the cell wall more bioavailable, algae biomass must be treated before fermentation. We submitted Kappaphyccus alvarezzi macroalgae biomass to autoclave (at 120 °C and 1 atm for 6 h) treatment and/or enzymatic (Celluclast® and/or a recombinant β- glucosidase) hydrolysis, to break down complex carbohydrates into available sugars that were used to produce H2 by fermentation. Macroalgae biomass treated with Celluclast®+β-glucosidase and with combined thermal treatment and enzymatic hydrolysis reached very similar TRS productivities, 0.24 and 0.22 g of TRS/L.h, respectively. The enzymatically treated biomass was employed as feedstock to produce H2 by Clostridium beijerinckii Br21, which afforded high yield: 21.3 mmol of H2/g of dry algae biomass. Hence, treatment with Celluclast® and recombinant β-glucosidase provided macroalgae biomass for enhanced bioconversion to H2 by C. beijerinckii Br21. Keywords: Kappaphyccus alvarezzi, Clostridium beijerinckii, Biohydrogen, Cellulase, β-glucosidase
Highlights
Nowadays, one of the most important environmental issues is to replace finite, polluting fossil fuels with sustainable fuels [1,2]
Samples of the algae suspensions collected after autoclave treatment and enzymatic hydrolysis were filtered through 0.45-μm acetate cellulose membrane before analytical determinations were carried out
The length of the carbohydrate products formed after autoclave treatment and after enzymatic hydrolysis with the two enzymes was analyzed by thin layer chromatography (TLC)
Summary
One of the most important environmental issues is to replace finite, polluting fossil fuels with sustainable fuels [1,2] In this context, hydrogen (H2) is an alternative fuel to the traditional ones: H2 combustion produces water only, and this fuel has three times higher energy potential than gasoline (142 kJ.g-1) [1,3,4,5]. Physical-chemical methods, which depend on fossil fuels or require a large amount of energy, are mainly employed to obtain H2 [4]. Biological routes, such as fermentation, can be used to obtain H2 [1,3]. Compared to higher plant biomass, algae offer a number of potential advantages: 1) they convert sunlight to biochemical energy more efficiently than terrestrial plants; 2) they grow on vast tracts of sea by action of sunlight only, without the need for fertilizers; 3) their production does not depend on arable land availability, so their cultivation does not compete with food production; 4) they consume CO2, thereby helping to reduce greenhouse gas emissions; and 5) they do not contain lignin, which simplifies biomass saccharification processes for further use in fermentation [6-16]
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