Sequential chemical and enzymatic pretreatment of palm empty fruit bunches for Candida pelliculosa bioethanol production

Abstract

Second-generation bioethanol production process was developed using pretreated empty fruit bunches (EFB). Consecutive acid/alkali EFB pretreatment was performed, first with HCl and then with NaOH with final washing steps for phenolic compounds elimination. Scanning electron microscopy images showed that EFB chemical treatments indeed attacked the cellulose fibers and removed the silica from surface pores. The optimization of enzymatic hydrolysis of EFB's cellulosic fraction was performed with 0.5%-4% v/v of Cellic R CTec2/Novozymes, different EFB concentrations (5%-15%, w/v), and hydrolysis time (6-72 H). Optimization essays were carried out in Erlenmeyer flasks and also in a 1 L stirred tank reactor. After enzymatic hydrolysis, a hydrolysate with 66 g/L of glucose was achieved with 2.2% (v/v) Cellic R CTec2, 15% (m/v) acid/alkaline pretreated EFB after 39 H of hydrolysis. A gain of 11.2% was then obtained in the 1 L stirred tank promoted by the agitation (72.2 g/L glucose). The hydrolysate was employed in bioethanol production by a new isolate Candida pelliculosa CCT 7734 in a separate hydrolysis and fermentation process reaching 16.6 and 23.0 g/L of bioethanol through batch and fed-batch operation, respectively. An integrated biorefinery process was developed for EFB processing chain.

Simultaneous Saccharification and Fermentation of Empty Fruit Bunches of Palm for Bioethanol Production Using a Microbial Consortium of S. cerevisiae and T. harzianum

“…The previous study by Burhani et al [46] obtained 90.5% cellulose, no trace of hemicellulose, and 9.13% lignin after the pretreatment process. In a study by Campioni et al [47], it was reported that there was an increase in EFB cellulose content after acid-alkali pretreatment from 42.2 to 62.6%. Different authors observed different EFB compositions obtained after the acid-alkali pretreatment process.…”

“…The sequence of pretreatment in combined form gave a high impact on reducing sugar production by increasing the cellulose and reducing the hemicellulose and lignin content [58]. In the work performed by Campioni et al [47], EFBs' cellulose content was increased from 42.2 to 62.6% after acid and alkali treatment, while their hemicellulose component had a mass loss of about 90% and a lignin loss of about 25%.…”

Biofuels Production from Renewable Resources

“…On the same matrix (palm empty fruit bunches or EFB), Campioni et al. [2] propose an integrated biorefinery process. This approach exploits a sequence of steps involving chemical pretreatment, enzymatic saccharification, and glucose fermentation in a separate hydrolysis and fermentation.…”