問題詳情

Reading test article 2 (source: Cellulose 2014, 21(l):835-844)Cellulose, a (3-1，4 linkage polysaccharide, which is the most abundant material on earth (Brown2004)，can be acquired from plants，microorganisms (Ohad et al. 1962), and animals (Sturcova et al.2005). Although plant cellulose (PC) and bacterial cellulose (BC) possess the same molecular structure, BC exhibits the unique physical properties at nanoscale network (Yamanaka et al. 3 989; Nishi et al. 1990) (i.e. high water content and high tensile strength (Tanpichai et al. 2012))，and does not require extra processing steps to remove impurities such as lignin, pectin, and hemicellulose. Accordingly, BC has been adopted as biomaterials of wound dressing (Portal et al. 2009)，low calorie foods (Okiyama et al. 1992), and composite papers (Brown 2004; Cheng et al. 2011; Trovatti et al. 2012).Many bacteria can produce BC including Achromobacter, Alcaligenes, Gluconaceiobacter, Aerobacter, Agrobacterium, Azotobacter, Pseudomonas, Rhizobium, and Sarcin (Brown .2004; Deinema and Zevenhui 1971). However, only Gluconacetobacter xylinum (G. xylinwn) can produce BC at commercially viable level due to its high productivity.A rotating disk bioreactor with plastic composite support (PCS) as the solid support was evaluated for BC production. Results demonstrated that BC can be produced in a semi-continuous manner. The BC productivity reached around 2.58 mg/cm2/day and can be sustained for at least five consecutive runs. Scanning electron microscopy results confirmed that Gluconacetobacter can attach on the PCS surface, which eliminates the need of reinoculation. X-ray diffraction patterns and mechanical analysis of BC produced from this semi-continuous process exhibited lower crystallinity (66.9 %) and mechanical property (Young’s modulus of 372.5 MPa) when compared with the BC obtained from static culture (crystallinity= 88.7 %, Young’s modulus of 3955.6 MPa). Both BC samples possessed similar water content (98.66% vs. 99.04%) and thermostability (around 346°C). In conclusion, the PCS rotating disk bioreactor system can be used to produce BC in pellicle form with enhanced productivity and, meanwhile，can be scaled up easily to meet commercial need.
10. What’s the linkage between cellulose units?
(A) p-1, 3 linkage,
(B) p~l, 6 linkage,
(C) p~1, 4 linkage,
(D) a -1, 4 linkage.

參考答案

答案：[無官方正解]
難度：適中0.5
統計：A(0),B(0),C(0),D(0),E(0)

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