Rotary biofilm reactor: A new tool for long-term bioethanol production from non-sterilized beet molasses by Saccharomyces cerevisiae in repeated-batch fermentation. (1st June 2020)

• Record Type: Journal Article
• Authors: Roukas, Triantafyllos; Kotzekidou, Parthena
• Is Part Of: Journal of cleaner production. Volume 257(2020)
• Publication Date: 2020-06-01
• Subjects: Rotary biofilm reactor -- Bioethanol -- Beet molasses -- Saccharomyces cerevisiae -- Repeated-bath fermentation -- Energy indicators; Factory and trade waste -- Management -- Periodicals; Manufactures -- Environmental aspects -- Periodicals; Déchets industriels -- Gestion -- Périodiques; Usines -- Aspect de l'environnement -- Périodiques; 628.5
• DOI: 10.1016/j.jclepro.2020.120519
• Languages: English
• ISSNs: 0959-6526

Abstract

Abstract: A new tool was developed for second generation ethanol production from non-sterilized beet molasses to energy recovery from the agro-industrial byproduct. The rotary biofilm reactor (RBR) used in repeated-batch fermentation for long-term bioethanol production showed high energy recovery efficiency. This study will serve as a base line of initial studies in this field as no reports are available regarding the application of RBR for bioethanol production. Repeated-batch fermentations were carried out by replacement of the fermentation broth (3.5 L) by equal volume of fresh medium or with 15% and 30% recycling volume in RBR and the reactor without the discs. The fermentation was carried out under the following conditions: an inoculum concentration of 5.6 g dry baker's yeast/L, initial sugar concentration of 15% (w/v), initial pH 5.0, temperature 30 °C, and rotation speed of 40 rpm. The high bioethanol concentration (average value 52.3 g/L) and the average bioethanol productivity (1.45 g/L/h) were stable for 60 days by recycling 30% of the volume of the broth every 36 h in repeated-batch fermentation using the RBR. The energy evaluation data indicated a positive energy balance with an energy ratio of 1.63 MJ/MJ. The other energy indicators such as energy consumption, energy conversion, energy yield, and energy recovery were 16.5 MJ/kg bioethanol produced, 4.7 MJ/kg beet molasses, 1.3 MJ/100 g sugar utilized, and 84.8%, respectively. The results showed that non-sterilized beet molasses is a promising feedstock for bioethanol production in industrial scale by Saccharomyces cerevisiae using the RBR and this process is considered energetically feasible. Graphical abstract: Image 1084 Highlights: Rotary biofilm reactor enhanced bioethanol production from non-sterilized molasses. Bioethanol production of 52.3 g/l was achieved for 60 days in repeated-batch culture. The process was energetically feasible with an energy ratio of 1.63 MJ/MJ. The energy conversion was 4.7 MJ/kg beet molasses. Bioethanol yield (49%) and energy recovery (84.8%) were achieved for 60 days.