Continuous sodium hydroxide‐catalyzed pretreatment of empty fruit bunches (EFB) by continuous twin‐screw‐driven reactor (CTSR)

Abstract

BACKGROUND: Since extrusion has many desirable characteristics such as high shear, rapid mixing, short residence time, controllable barrel temperature, and adaptability to process modification, the technology has been applied as a viable continuous pretreatment method for empty fruit bunches (EFB). RESULTS:Optimized conditions for a continuous twin-screw-driven reactor (CTSR) were determined to be 170 • C barrel temperature, 1.6% (w/v) sodium hydroxide, 1:8 solid to liquid ratio, and 5 rpm screw rotational speed. Under these operating conditions, 56.55% of lignin and 39.18% of hemicellulose fractions were solubilized from raw EFB, which increases the glucan content in pretreated EFB from 39.25% to 53.60%. After subsequent 48-h enzymatic hydrolysis of pretreated EFB, the highest digestibility of 92.4% was achieved with an enzyme loading of 30 FPU g −1 -glucan for cellulase and 70 pNPG g −1 -glucan for β-glucosidase.CONCLUSION: CTSR processing has great potential for increasing the efficiency of EFB pretreatment compared with batch pretreatments.

Biorefinery of the Olive Tree—Production of Sugars from Enzymatic Hydrolysis of Olive Stone Pretreated by Alkaline Extrusion

“…Extrusion alone is a mechanical process that provides high shear, fast heat transfer and thorough mixing [20] and the possibility to combine it with other pretreatments adds interest to the process application [21,22]. Chemical reagents and biocatalysts can also be added during extrusion [17,[23][24][25], resulting in a mixture of physical, thermal, chemical and/or biological effects that enhance the disruption of the lignocellulosic matrix. Among the different process possibilities, extrusion combined with an alkaline chemical agent (most notably NaOH) has been proven to be successful operating at moderate temperatures and pressures and causing no or very low sugar degradation compared to other chemical pretreatments [19,26].…”

Study of the Application of Alkaline Extrusion to the Pretreatment of Eucalyptus Biomass as First Step in a Bioethanol Production Process

“…The amount of sugars recovered in the filtrate is in any case the same. Supporting these findings, Choi et al [33] found that the glucan content in the extrudate increased and the lignin content decreased as the L/S ratio increased from 4 to 8 for the alkaline pretreatment of empty fruit bunches, especially at high NaOH loadings (>5% NaOH/DM).…”

“…Other authors have reported deacetylation and/or delignification in alkaline extrusion of different biomasses. For example, Choi et al [33] extruded empty fruit bunches at high temperature (170 • C) and low screw speed (5 rpm) and found that, as the amount of catalyst increased from 5% to 20% NaOH/DM, the glucan content in the extrudate increases, corresponding to a decrease of the hemicellulosic sugars and lignin due to solubilization. Similar behavior was reported by Han et al [35] and Duque et al [27] on alkali-extruded barley straw.…”

An Overview of Extrusion as a Pretreatment Method of Lignocellulosic Biomass

“…Screw speeds less than 100 rpm are considered low and those above 120 rpm are considered high. In particular cases, it can be set very low (down to 5 rpm), or very high (up to 420 rpm) [59,68,115,116]. As noted in the preview sections, screw speed influences the torque, the SME, the barrel temperature, the residence time, and the substrate flow rate.…”