High Solid-Loading Pretreatment/Saccharification Tests with CaCCO (Calcium Capturing by Carbonation) Process for Rice Straw and Domestic Energy Crop, Erianthus arundinaceus

Abstract

The CaCCO process (Park et al., 2010), a sugar platform for herbaceous lignocellulosics, was modified and evaluated for fermentable-sugar recovery in solution, using rice straw (RS) as well as stems and leaves of Erianthus arundinaceus (ER), one of the strategic energy crops in Japan. Continuous wet milling of a mixture of feedstock, water and Ca(OH)2, with a weight ratio of 3/7/0.3, was adopted, not only to evaluate the applicability for wet feedstocks, but also for simultaneous Ca(OH)2 mixing with the milled feedstocks. We also applied low temperatures of 95 100 C for the alkali pretreatment to save energy. Enzymatic-saccharification tests were performed for the pretreatment slurries from 10 kg feedstocks for 72 h at 40 C under a CO2-pressurized atmosphere at 0.9 MPa with high-solid loadings of 28.4% (w/w) for RS and 27.8% (w/w) for ER. These tests successfully solubilized 80.6% (RS) and 68.1% (ER) of the total glucose-and xylose residues in the solids. Following centrifugation, the solubilized-sugar concentrations in the recovered solutions were 16.9% (w/v) for RS and 15.5% (w/v) for ER. Thus, we demonstrated that the CaCCO process could be a simple and flexible platform for preparation of dense sugar solutions from dry-and wet feedstocks, which could stimulate a new agricultural bio-industry for vitalizing rural areas.

Washing Lime-Pretreated Rice Straw with Carbonated Water Facilitates Calcium Removal and Sugar Recovery in Subsequent Enzymatic Saccharification

“…Further pressurization with CO 2 would reduce the reaction pH, leading to better sugar recovery ratios. 11) …”

“…We developed the “Calcium Capturing by Carbonation” (CaCCO) process in which the pH of the slurry after Ca(OH) 2 pretreatment of feedstock is lowered by pressurization by CO 2 gas as acid for saccharification at a pH below 6.5. 8) 9) 10) 11) Although the pressure of CO 2 needed for appropriate pH control depends on the amount of residual calcium in the slurry, the washing step could affect saccharification efficiency in CaCCO at a specific CO 2 pressure value. In this study, we also examined the possibility of simplification of CaCCO by using pretreated, washed feedstock for saccharification in a CO 2 atmosphere.…”

Reusable Floating Beads with Immobilized Xylose-Fermenting Yeast Cells for Simultaneous Saccharification and Fermentation of Lime-Pretreated Rice Straw

“…Pre-saccharified RS slurry was prepared according to our previously reported method. 19) Chopped RS (10 kg) was mixed with 1 kg of Ca(OH) 2 and 23 L of distilled water, and the mixture was crushed using a wet-milling machine (Shokusenki, Shinko Engineering Co. Ltd., Gifu, Japan). The milled mixture was placed in an autoclave bag (Thermo Fisher Scientific Inc., Pittsburgh, USA) prior to heating at 95 °C for 1 h in a high-pressure steam sterilizer (KS-323, Tomy Seiko Co. Ltd.).…”

Evaluation of the Enzymatic Saccharification Efficiency of an Energy Crop, <i>Erianthus arundinaceus</i>, Pretreated with Ca(OH)₂ Using both Countercurrent Washing System and pH Adjustment by Nonpressurized CO₂

“…Considering the production of fermentable sugars in Japan, the combination of various biomass resources harvested through different seasons, such as RS and stem and leaves of Erianthus arundinaceus (ER), has been recommended to minimize the storage period. 3) Ike et al 4) have proposed a method for the enzymatic saccharification of these two raw resources under pressurized conditions after a pretreatment with calcium hydroxide (Ca(OH) 2 ) followed by a carbon dioxide neutralization. In this process, for the needs of year-round supply with raw materials, it is assumed that the harvested plant resources will be used either directly, without storing, or they will be stored under the dry storage conditions.…”