Abstract
This paper evaluated the effectiveness of nitric acid pretreatment on the hydrolysis and subsequent fermentation of Jerusalem artichoke stalks (JAS). Jerusalem artichoke is considered a potential candidate for producing bioethanol due to its low soil and climate requirements, and high biomass yield. However, its stalks have a complexed lignocellulosic structure, so appropriate pretreatment is necessary prior to enzymatic hydrolysis, to enhance the amount of sugar that can be obtained. Nitric acid is a promising catalyst for the pretreatment of lignocellulosic biomass due to the high efficiency with which it removes hemicelluloses. Nitric acid was found to be the most effective catalyst of JAS biomass. A higher concentration of glucose and ethanol was achieved after hydrolysis and fermentation of 5% (w/v) HNO3-pretreated JAS, leading to 38.5 g/L of glucose after saccharification, which corresponds to 89% of theoretical enzymatic hydrolysis yield, and 9.5 g/L of ethanol. However, after fermentation there was still a significant amount of glucose in the medium. In comparison to more commonly used acids (H2SO4 and HCl) and alkalis (NaOH and KOH), glucose yield (% of theoretical yield) was approximately 47–74% higher with HNO3. The fermentation of 5% nitric-acid pretreated hydrolysates with the absence of solid residues, led to an increase in ethanol yield by almost 30%, reaching 77–82% of theoretical yield.
Highlights
According to forecasts by the International Energy Agency (IEA), as the population increases (1.3-fold) between 2009 and 2050, energy consumption will grow even more quickly (2-fold), reaching15–18 billion tons of oil equivalent (TOE) in 2035 [1,2]
This study investigated the effect of different alkaline and acidic pretreatments, on the yields of subsequent enzymatic hydrolysis and fermentation
To evaluate the potential of Jerusalem artichoke stalks (JAS) as a feedstock for second generation bioethanol production, the biomass was analyzed for total solids [37], cellulose [38], hemicellulose [39], and lignin content [40]
Summary
According to forecasts by the International Energy Agency (IEA), as the population increases (1.3-fold) between 2009 and 2050, energy consumption will grow even more quickly (2-fold), reaching15–18 billion tons of oil equivalent (TOE) in 2035 [1,2]. According to forecasts by the International Energy Agency (IEA), as the population increases (1.3-fold) between 2009 and 2050, energy consumption will grow even more quickly (2-fold), reaching. Due to the depletion of coal, oil, and natural gas reserves, as well as increasing public awareness of the environmental impact of emissions, more attention is being focused on developing renewable energy sources, such as biofuels [3]. First-generation biofuels are mostly produced from starch- and sugar-based biomass, derived from food crops grown on agricultural land using standard processes. This can affect food supply and prices. Interest has been growing in second generation biofuels, produced using different feedstocks
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