Fermentation efficiency of intermediates and by-product of sugar beet processing

Abstract

Sugar beet is a highly selected crop that accumulates 70% of sugar in the roots, while the other 30% is made up of non-sugars, of which more than 20% are water-insoluble cell walls. The applied processing technology affects the chemical composition of intermediate products and by-products. Therefore, all major global sugar industry concerns pay special attention to regular monitoring of the quality of intermediate production products (juices) and by-products (molasses), whether viewed from the aspect of technological process control or the aspect of an application in fermentation processes. The intermediate products of sugar beet processing contain fermentable sugars, which can be directly used for fermentation without any additional modification, and compared to all other sources of carbohydrates, very suitable raw materials for the production of bioethanol, both from a technological and an economic point of view. Based on the above, this research aimed to determine the fermentation efficiency in bioethanol production using the intermediate products and by-product of sugar beet processing. Therefore, the experiments were performed using raw, thin, and thick juice and molasses. Furthermore, since molasses is a traditional raw material for bioethanol production, it was used as a "reference" in analyzing the fermentation efficiency of raw, thin, and thick juice. The intermediate products used to prepare the fermentation medium were diluted with water to the final concentrations of fermentable sugars. Raw and thin juice were used as fermentation media with the maximum sugar concentration contained in the juice delivered from the factory and with dilutions of 50 and 100 grams of fermentable sugars per liter of fermentation medium. Thick juice and molasses were diluted to final concentrations of fermentable sugars of 50, 100, 150, 200, and 250 g/L. Fermentation efficiency (%) was defined as the amount of consumed fermentable sugars per 100 g of the initial amount of sugar. With raw juice, the fermentation efficiency has higher values than those obtained with molasses for all three applied initial concentrations of fermentable sugars. The highest fermentation efficiency was achieved using thin juice at an initial concentration of fermentable sugars of 13% (m/v). The fermentation efficiency of a medium with thick juice is significantly higher than that of a medium with molasses in the examined interval of initial concentrations of fermentable sugars from 5 to 25% (m/v).