Integrated hydrolysation and fermentation of the fresh sugar beet pulp to bioethanol

Pulpa šećerne repe obilan je otpadni industrijski materijal koji predstavlja velik potencijal za proizvodnju bioetanola jer sadrži velike količine celuloze, hemiceluloza i pektina. Kemijska i strukturna robustnost pulpe šećerne repe ograničava prinos fermentabilnih šećera dobivenih hidrolizom pa zbog toga čini “usko grlo” proizvodnje bioetanola. Fizikalne metode predobrade koje su uključivale ultrazvuk i termilnu obradu, testirane su i korištene uz enzimsku hidrolizu uz pomoć celulaza i pektinaza kako bi se odredio najučinkovitiji način predobrade pulpe šećerne repe. Tijekom istraživanja evaluirane su različite kombinacije spomenutih metoda predobrade. Metodom predobrade ultrazvukom oslobađa se rezidualna saharoza, dok metoda termičke predobrade pojačava učinkovitost enzimske obrade, posebno hidrolize celuloznih, hemiceluloznih i pektinskih komponenti u glukozu, galaktozu, arabinozu i galaktouronsku kiselinu. Optimizirani proces hidrolize kombiniran je sa fermentativnim stupnjem procesa korištenjem Saccharomyces cerevisiae za proizvodnju etanola u bioreaktoru.Sugar beet pulp is an abundant industrial waste material which holds a great potential for bioethanol production due to its high content of cellulose, hemicelluloses and pectin. Its structural and chemical robustness limits the yield of fermentable sugars obtained by hydrolysation and is therefore the bottleneck for bioethanol production. Physical (ultrasound and thermal) pre-treatment methods were tested and combined with enzymatic hydrolysis by cellulase and pectinase to evaluate the most efficient strategy. Various combinations of the pre-treatment methods were evaluated. Sonication pretreatment favors the release of residual sucrose whereas thermal pretreatment enhances the effectiveness of the enzymatic treatment, especially the hydrolysis of cellulosic, hemicellulosic and pectinic components into glucose, galactose, arabinose and galacturonic acid. The optimized hydrolysis process was combined with a fermentative step using Saccharomyces cerevisiae for ethanol production in a single bioreactor