Yamagishi Kenji, Ike Masakazu, Guan Di, Tokuyasu Ken
1 Bioresource Conversion Unit, Food Research Institute, National Agriculture and Food Research Organization.
J Appl Glycosci (1999). 2019 Jan 20;66(1):11-19. doi: 10.5458/jag.jag.JAG-2018_0003. eCollection 2019.
Generally, Ca(OH) pretreatment of lignocellulosics for fermentable sugar recovery requires a subsequent washing step for calcium removal and pH control for optimized saccharification. However, washing Ca(OH)-pretreated feedstock with water is considered problematic because of the low solubility of Ca(OH) and its adsorption to biomass. In this study, we estimated the availability of carbonated water for calcium removal from the slurry of Ca(OH)-pretreated rice straw (RS). We tested two kinds of countercurrent washing sequences, four washings exclusively with water (W4) and two washings with water and subsequent two washings with carbonated water (W2C2). The ratios of calcium removal from pretreatment slurry after washing were 64.2 % for the W4 process and 92.1 % for the W2C2 process. In the W2C2 process, 49 % of the initially added calcium was recovered as CaO by calcination. In enzymatic saccharification tests under a CO atmosphere at 1.5 atm, in terms of recovery of both glucose and xylose, pretreated, feedstock washed through the W2C2 process surpassed that washed through the W4 process, which could be attributed to the pH difference during saccharification: 5.6 in the W2C2 process 6.3 in the W4 process. Additionally, under an unpressurized CO atmosphere at 1 atm, the feedstock washed through the W2C2 process released 78.5 % of total glucose residues and 90.0 % of total xylose residues. Thus, efficient removal of calcium from pretreatment slurry would lead to not only the recovery of added calcium but also the proposal of a new, simple saccharification system to be used under an unpressurized CO atmosphere condition.
一般来说，为了回收可发酵糖而对木质纤维素进行氢氧化钙预处理后，需要后续的洗涤步骤来去除钙并控制pH值，以实现最佳糖化效果。然而，用水洗涤经氢氧化钙预处理的原料被认为存在问题，因为氢氧化钙的溶解度低且会吸附到生物质上。在本研究中，我们评估了碳酸水从氢氧化钙预处理稻草（RS）浆料中去除钙的可行性。我们测试了两种逆流洗涤顺序，即仅用水进行四次洗涤（W4）以及先用水洗涤两次，随后用碳酸水洗涤两次（W2C2）。洗涤后从预处理浆料中去除钙的比例，W4工艺为64.2%，W2C2工艺为92.1%。在W2C2工艺中，最初添加的钙有49%通过煅烧回收为氧化钙。在1.5个大气压的CO气氛下进行的酶糖化试验中，就葡萄糖和木糖的回收率而言，经W2C2工艺洗涤的预处理原料超过了经W4工艺洗涤的原料，这可能归因于糖化过程中的pH差异：W2C2工艺中为5.6，W4工艺中为6.3。此外，在1个大气压的非加压CO气氛下，经W2C2工艺洗涤的原料释放了78.5%的总葡萄糖残基和90.0%的总木糖残基。因此，从预处理浆料中有效去除钙不仅会导致添加钙的回收，还会提出一种在非加压CO气氛条件下使用的新型简单糖化系统。
