Statistical optimization of pretreatment of orange processing waste using response surface methodology for bioethanol production

• Published in: Energy sources. Part A, Recovery, utilization, and environmental effects Recovery, utilization, and environmental effects, 2021-08, Vol.ahead-of-print (ahead-of-print), p.1-15
• Main Authors: Aissi, Fatma Zohra, El Hadi, Djamel, Megateli, Smain, Ketfi, Sabrina
• Format: Article
• Language: English
• Subjects: bioethanol; optimization; Orange processing waste; pretreatment; total sugar yield
• ISSN: 1556-7036; 1556-7230
• DOI: 10.1080/15567036.2021.1967519

This study aims to maximize total sugar yield of two varieties of sweet orange processing waste OPW: Valencia Late and Double fine. They were collected from two different Algerian juice factories. The initial total sugar yield of both varieties was 49.33 ± 0.78% and 44.04 ± 1.32%, respectively. Therefore, statistical optimization of the pretreatment of orange processing waste powder OPWP was established using sulfuric acid and steam explosion to achieve a high-level rate of total sugar from OPWP. The acid hydrolysis steam explosion used in this study due of its efficiency and simplicity. The hydrolysis factors, such as acid (0.25%, 0.50% and 0.75%), solid loading (2%, 6% and 10%) and time (10 min, 20 min and 30 min), were further optimized using response surface methodology. Results revealed that the yield of total sugar was 74.57% and 70.70% dry weight for Valencia Late and Double fine respectively. The optimized conditions were obtained by 0.5% v/v acid, 2% w/v OPWP and 20 min residence time. The derived regression model shows a strong positive relationship between the obtained yield and the variables with a coefficient of determination (R 2 ) values of 0.9219 and 0.9367 for Valencia Late and Double fine, respectively. Furthermore, scanning electron microscopy, Fourier transform infrared, X-ray diffraction and thermogravimetric analysis for comparison of untreated and pretreated material confirms that the pretreatment is a crucial step to enhance the total sugar yield, solubilize hemicellulose and remove lignin. These results appear to be a promising source of carbohydrates for producing bioethanol.