Abstract
The energy-saving glucose production process from starchy sources was developed by replacing high-temperature, liquid-phase by low-temperature, solid-phase. Therefore, the enzymatic hydrolysis under gelatinization temperature at very high gravity (≥300 g.L−1) of starchy substrates presents as an emerging technology. This study focused on the hydrolysis kinetics of cassava flour affected by different pretreatment methods. Cassava flour (dried, milled) was prepared in acetate buffer (pH 4.2) with starch concentration ranging from 10–30% (w/w). The mash was then pre-treated by three different methods for 30 min using heating (30, 40, 50 °C), enzyme (Viscozyme L 0.1% w/w) and microwave (3 × 20 s at 800 W). The suspension was then hydrolyzed with Stargen 002 (0.2% w/w) at 30 °C for 48 h. The enzyme adsorption kinetics was described by the Langmuir isotherm equation. The pretreatments at 50 °C and with enzyme resulted in the highest efficiency with the hydrolysis yield ranging from 76–79% after 48 h. The hydrolysis yield decreased to 67% (using microwave), 66% (at 45 °C), 61% (at 40 °C) and 59% (at 30 °C). The linear relationship between enzyme adsorption and produced glucose was demonstrated. The kinetics of glucose production was fitted by an empirical equation (analogy with Michaelis-Menten model) and allowed predicting the maximum hydrolysis yield.
Highlights
In an effort to combat climate change, aid energy independence, and to counteract diminishing supplies of fossil fuels, there has been a resurgence of research on renewable energy sources
The costs due to the high energy demand of starch-based sugar production could be reduced if enzymatic hydrolysis of starch is performed at temperatures below the onset of gelatinization at, for example, 54 ◦ C for wheat, 60 ◦ C for potato, or 65 ◦ C for maize [3]
The objectives of this research were to; (i) investigate the effect of various pretreatment methods on amylolysis of granular starch from cassava flour; (ii) explain these impacts by studying the kinetics of enzyme adsorption onto starch granule; and (iii) model the kinetics of glucose production to predict the maximum yield which can be obtained for different hydrolysis conditions
Summary
In an effort to combat climate change, aid energy independence, and to counteract diminishing supplies of fossil fuels, there has been a resurgence of research on renewable energy sources. Bio-ethanol becomes one of the most common and important alternatives to replace fossil fuel resources. It is normally produced by the microbial conversion (common fermentation by yeast) of plant biomass (starchy or/and cellulosic raw materials) [1]. The conventional starch-based sugar production technology presents a high energy demand from fossil sources for two separated steps: liquefaction (95–105 ◦ C) and saccharification (60–65 ◦ C). The costs due to the high energy demand of starch-based sugar production could be reduced if enzymatic hydrolysis of starch is performed at temperatures below the onset of gelatinization at, for example, 54 ◦ C for wheat, 60 ◦ C for potato, or 65 ◦ C for maize [3]. Beside the effect of botanical origin of starch [4], several factors strongly influence the hydrolysis of native starch such as particle size, crystallinity, mass
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