Abstract
BackgroundAlgal biomass, known as a potential feedstock for biofuel production, has cell wall structures that differ from terrestrial biomass. The existing methods for processing algae are limited to conventional pretreatments for terrestrial biomass. ResultsIn this study, we investigated a novel hydroxyl radical-aided approach for pretreating different types of algal biomass. In this process, hydroxyl radicals formed by a Fenton system were employed in combination with heating to alter the crystalline structure and hydrogen bonds of cellulose in the algal biomass. FeSO4 and H2O2 at low concentrations were employed to initiate the formation of hydroxyl radicals. This method releases trapped polysaccharides in algal cell walls and converts them into fermentable sugars. The effects of temperature, time, and hydroxyl radical concentration were analyzed. The optimal pretreatment condition [100 °C, 30 min, and 5.3 mM H2O2 (determined FeSO4 concentration of 11.9 mM)] was identified using a central composite design. Complete (100 %) carbohydrate recovery was achieved with some algal biomass without formation of inhibitors such as hydroxymethylfurfural and furfural as by-products. Both microalgal and macroalgal biomasses showed higher enzymatic digestibility of cellulose conversion (>80 %) after the milder pretreatment condition.ConclusionHydroxyl radical-aided thermal pretreatment was used as a novel method to convert the carbohydrates in the algal cell wall into simple sugars. Overall, this method increased the amount of glucose released from the algal biomass. Overall, enhanced algal biomass digestibility was demonstrated with the proposed pretreatment process. The new pretreatment requires low concentration of chemical solvents and milder temperature conditions, which can prevent the toxic and corrosive effects that typically result from conventional pretreatments. Our data showed that the advantages of the new pretreatment include higher carbohydrate recovery, no inhibitor production, and lower energy consumption. The new pretreatment development mimicking natural system could be useful for biochemical conversion of algal biomass to fuels and chemicals.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-015-0372-2) contains supplementary material, which is available to authorized users.
Highlights
Algal biomass, known as a potential feedstock for biofuel production, has cell wall structures that differ from terrestrial biomass
The present study investigated the effects of processing variables, including hydroxyl radical concentration, pretreatment time, and pretreatment temperature, on the glucose production of different types of algal biomass
Hydroxyl radical-aided thermal pretreatment was used as a novel method to disrupt the hydrogen bonds and cellulose crystallinity in algal biomass, which is beneficial to conversion of the carbohydrates in the algal cell wall into simple sugars by enzymolysis process
Summary
Known as a potential feedstock for biofuel production, has cell wall structures that differ from terrestrial biomass. The cellulose conversion of macroaglae reached 83.37 % [6] Numerous inhibitors, such as hydroxymethylfurfural (HMF), 2-furfural, and acetic acid, were formed in hydrothermal pretreatment at 200 °C, wet oxidation pretreatment using 12 bars of O2 at 200 °C, and steam explosion pretreatment [7], besides acid or alkali pretreatment for algal biomass. These inhibitors may affect the downstream production of highvalue algae products. A new pretreatment technology is urgently needed for algal comprehensive utilization with low cost and low energy
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