Integrated Ozonation-Enzymatic Hydrolysis Pretreatment of Sugarcane Bagasse: Enhancement of Sugars Released to Expended Ozone Ratio

Abstract

The combined effects of three key ozonation process parameters on the integrated ozonation-enzymatic hydrolysis pretreatment of sugarcane bagasse (SCB) were investigated, with emphasis on the relationship between sugar release and ozone consumption. A lab-scale fixed bed reactor was employed for ozonation at varying ozone doses (50, 75 and 100 mg O3/g SCB), particle sizes (420, 710 and 1000 µm) and moisture contents (30, 45 and 60% w/w) in multifactorial experiments, keeping a residence time of 30 min. The ozonated SCB showed a reduction in the content of acid-insoluble lignin from 26.6 down to 19.1% w/w, while those of cellulose and hemicellulose were retained above 45.5 and 13.6% w/w, with recoveries of 100–89.9 and 83.5–72.7%, respectively. Ozone-assisted enzymatic hydrolysis allowed attaining glucose and xylose yields as high as 45.0 and 37.8%, respectively. The sugars released/ozone expended ratio ranged between 2.3 and 5.7 g sugars/g O3, being the higher value achieved with an applied ozone input of 50 mg O3/g SCB and SCB with 420 µm particle size and 60% moisture. Such operating conditions led to efficient ozone utilization (<2% unreacted ozone) with a yield of 0.29 g sugars/g SCB. Overall, the amount of sugars released relative to the ozone consumed was improved, entailing an estimated cost of ozonation of USD 34.7/ton of SCB, which could enhance the profitability of the process.

Role of advanced oxidation processes in lignocellulose pretreatment towards biorefinery applications: a review on emerging trends and economic considerations

“…The synthesis of ozone demands a high energy input (36 MJ kg −1 of ozone) and large doses for pretreatment (9 kg O 3 per ton dry biomass) to create 63 kg ethanol. According to the research by Osuna-Laveaga et al , 118 much greater ozone dosages of 100–300 kg O 3 per ton dry biomass were required to provide a sugar yield of40–50%. Therefore, the energy input and ozone consumption in ozone oxidation must be reduced for it to become a sustainable and feasible pretreatment method.…”

Chemical and Structural Changes of Ozonated Empty Fruit Bunch (EFB) in a Ribbon-Mixer Reactor

“…The subsequent hydrolysis reaction could convert OTE to attain glucose yield as high as 45.09% [29] which can be used as feedstock for production of 5-hydroxymethylfurfural (5-HMF) [30] bioethanol [31], and levulinic acid (LA) [32]. The ozone pretreatment is proven to efficiently reduce the recalcitrance in EFB for the conversion of cellulose and enhancement of sugar release.…”

Determination of the lignin content of flax fiber with the acetyl bromide-ultraviolet visible spectrophotometry method

“…In previous studies, accurate testing methods for cellulose/hemicellulose (the National Renewable Energy Laboratory, NREL) and pectin (carbazole-vitriol colorimetry) were established. [22][23][24] However, none of the accepted analytical methods is considered to be a standard and unambiguous approach for determining lignin content, as these lignin detection methods generally suffer from under/overestimation of lignin content. 25 As a result, the challenge of accurately quantifying the lignin content in samples arises from the heterogeneity of the lignin composition and chemical structure.…”