White rot fungus Inonotus obliquus pretreatment to improve tran -1,4-polyisoprene extraction and enzymatic saccharificat
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White rot fungus Inonotus obliquus pretreatment to improve tran-1,4-polyisoprene extraction and enzymatic saccharification of Eucommia ulmoides leaves Shiyi Qian 1 & Chao Zhang 1 & Zhenduo Zhu 1 & Panpan Huang 1 & Xiangqun Xu 1 Received: 7 April 2020 / Accepted: 22 May 2020/ # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract
This study proposes an innovative strategy of lignocellulose biodegradation by Inonotus obliquus under solid-state fermentation in extracting Eucommia ulmoides trans-1,4-polyisoprene (EUG) and producing reducing sugars efficiently. EUG and sugars were obtained through the white rot fungal pretreatment of E. ulmoides leaves, ultrasound-assisted solvent extraction, and enzymatic saccharification. After mere 2-day fermentation, the loss of lignin, cellulose, and hemicelluloses of the leaves achieved 7.11%, 3.47%, and 6.44%, respectively due to the high activity levels of manganese peroxidase (MnP, 973 IU g−1) and lignin peroxidase (LiP, 1341 IU g−1) produced by the fungus. The breakdown of fibrous networks brought higher yields of EUG and reducing sugars. The highest extraction yield of EUG was 4.86% from the 2-day fermented leaves, 31.4% greater than that from the control (3.69%). Meanwhile, the leaf residues after EUG extraction released 97.8 mg g−1 reducing sugars with enzymatic saccharification, 77.5% greater than that from the control (55.1 mg g−1). The results demonstrated that I. obliquus could use E. ulmoides leaves as substrate to produce high-activity-level ligninolytic enzymes in a very short time and the lignocellulose selective degradation of E. ulmoides leaves enhanced the yields of EUG and reducing sugars. Keywords Eucommia ulmoides Oliver . Tran-1,4-polyisoprene . Inonotus obliquus . Lignocellulose degradation . Saccharification
Introduction Eucommia ulmoides Oliver (known as “Du-Zhong” in Chinese) belongs to a single species and genus in the plant family Eucommiaceae and is extensively cultivated in China. * Xiangqun Xu [email protected]
1
Key Laboratory of Plant Secondary Metabolism and Regulation of Zhejiang Province, College of Life Sciences and Medicine, Zhejiang Sci-Tech University, Hangzhou 310018, China
Applied Biochemistry and Biotechnology
E. ulmoides bark is widely used as one of the most precious traditional Chinese medicine (TCM) with a long history of safety for its kidney-tonifying function [1]. E. ulmoides not only is the TCM source, but can accumulate hard, fibrous long-chain trans-1,4-polyisoprene, known as EU gum or EU rubber (EUG) solely in almost all the plant tissues, for example leaves (1–5%), bark (6–10%), and pericarp of the seed (12–17%) [2]. As a biomaterial, EUG possesses excellent insulation, extremely low coefficient of thermal expansion, marvelous tensile strength, perfect breakage extensibility, effective tearing strength, and is resistant to acid and alkali [3]. Thanks to these outstanding characteristics, EUG has been widely applied in root canal fillings, golf balls, chutty, tires, conveyor belts, and submar
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