Wort disinfection treatment with electron beam for bioethanol production

Abstract

Microbial contamination of the wort during the fermentation process causes significant losses in ethanol production worldwide and creates a dependence of the industry on chemicals and antibiotics to control contamination. Therefore, this study used electron beam (e-beam) to disinfect wort from sugarcane (Saccharum officinarum L.) molasses and investigate the bioethanol fermentation. Four treatments (T0 -T3) were carried out using ionizing doses of radiation through the electron accelerator: 0 (control), 10, 20, and 40 kGy. Total mesophiles, total bacteria, sucrose, glucose, fructose, phenolics, flavonoids, hydroxymethylfurfural (5-HMF), and Furfural were measured. An alcoholic fermentation assay was performed after the irradiation process. The irradiated treatments showed no inversion of sugars and formation of the inhibitory by-products flavonoids, furfural and 5-HMF, except for the phenolic compounds. The lower dose tested (10 kGy) reduced more than 99.9 % of the total mesophiles and more than 99.99 % of the total bacteria in the substrate. In the fermentation, the irradiated worts presented similar (p > 0.05) yields (92, 93, and 94 %) and ethanol productivity levels (0.89, 0.88, and 0.87 g L -1 h -1 , for T1, T2, and T3 respectively). However, all treatments presented higher yields and productivity (p < 0.05) when compared to the control (88 % and 0.85 g L -1 h -1 ), highlighting the possible use of e-beam in wort fermentation at a lower dose (10 kGy). This allows reduction in losses caused by microbial contamination, besides increasing fermentation yield and productivity with lower energy consumption.

Electron Beam on Fermentation Medium as an Alternative Disinfection Method for Ethanol Distilleries: A Comprehensive Review

“…Furthermore, chemical compounds with bacteriostatic and bactericidal activities have been tested [49]. Recent studies have proposed the use of an electron beam as a disinfection treatment for sugarcane, corn and mixed worts [11,15,16]…”

“…Calegari et al (2023) [16] did not find the formation of flavonoids and aldehydes, such as furfural and 5-HMF, which are generally produced from sugar degradation, using doses of up to 40 kGy of electron beam [83]. The breakdown of carbohydrates, especially D-xylose, D-glucose and L-arabinose, may generate compounds such as phenolics [84], which are known to inhibit the biocatalyst [82,83].…”

“…Additional factors affect the susceptibility of vegetative cells to irradiation, such as the composition of the medium, moisture content, irradiation temperature and the presence or absence of oxygen, and whether the product is fresh or frozen can also have an impact [51,71,72]. Spores or endospores are resistant structures and tend to be more resilient than vegetative cells, often requiring higher doses of ionizing radiation for their inactivation [16]. In any case, the radiation dose applied must strike a balance between what can be tolerated in the product without undesirable changes and what is necessary to achieve the desired effects [50,65,72].…”

“…Recent studies have proposed the use of an electron beam as a disinfection treatment for sugarcane, corn and mixed worts [11,15,16]. However, to the best of our knowledge, there is no comprehensive literature review that evaluates the advantages and disadvantages of adopting this technology on an industrial scale for ethanol production.…”

Efeito da contaminação microbiana de amostras de matérias-primas no rendimento etanólico da fermentação.

“…O controle da carga microbiana por feixe de elétrons é um processo alternativo eficiente de descontaminação que pode ser instalado na linha de produção visando controlar a contaminação do mosto. Essa tecnologia é segura e requer um curto tempo de exposição à radiação ionizante (CALEGARI et al, 2023).…”