Abstract
The rising population and increasing demand for food place added pressure on the agricultural sector to maintain high process efficiency while implementing environmentally friendly methods. In this study, we investigate the effect of pre-hydrolysis of native rye starch and its influence on the yield of ethanol obtained by simultaneous saccharification and fermentation (SSF) from high gravity rye mashes with 25% and 28% w w−1 dry matter content. Fermentation was carried out in a 3-day system at a temperature of 35 ± 1 °C using the dry distillery yeast Ethanol Red (Saccharomyces cerevisiae). The characteristics of the tested raw material and changes in the native rye starch during enzymatic hydrolysis were analyzed using a scanning electron microscope (SEM). The SEM images revealed characteristic changes on the surface of the starch, which was found to have a layered structure, as well as interesting behavior by the yeast during SSF when the glucose concentration in the environment was lowered. Both in the mashes with 25% and 28% w w−1 dry matter, starch pre-hydrolysis did not significantly increase either the initial amounts of sugars available to the yeast or the fermentation efficiency and ethanol yield in comparison to the mashes without this pre-treatment.
Highlights
Starch is an important, common, and cost-effective renewable biopolymer
The present study investigates how the pre-hydrolysis of native starch affects the yield of ethanol obtained by simultaneous saccharification and fermentation (SSF) from high gravity rye mashes with 25% and 28% w w−1 dry matter (d.m.)
Samples were taken after 0 h and 72 h of fermentation to determine the content of reducing sugars and total sugars and dextrins The degree of starch saccharification (DSS) was calculated as the ratio of the reducing sugars to total sugars and expressed as a percentage
Summary
Common, and cost-effective renewable biopolymer. It is the main source of carbohydrates in human food and a specific energy store used for plant regeneration. This study proved that annealing treatment may be used as a way of increasing the degree of hydrolysis of tapioca and sweet potato starches at sub-gelatinization temperatures, using a raw starch hydrolyzing enzyme. A mixture of milled cereal grain and water (or hot plant effluents such as condensates or thin stillage) is heated to a temperature bellow starch gelatinization (for instance to 49–51 °C for rye grains) to improve the hydration of milled grains It is treated with acid alpha amylase to activate the starch granules (DuPont 2012). The suitability of ultrasonication for pre-gelatinization and the physicochemical properties of wheat and tapioca starches were investigated by Abedi et al (2019) Their results showed that the swelling and solubility of ultrasound-assisted pregelatinized starch increased as a function of the power, temperature, and time of treatment. The characteristics of the rye native grain and the progress of hydrolysis of the native starch during the SSF process were examined, using scanning electron microscopy (SEM)
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