細菌纖維素含水量與其電阻率、光學性質之關係

Abstract

細菌纖維素係由葡萄糖為單體所聚合成而成的立體奈米網狀結構，故鏈上有許多親水性的羥基，使其具有很高的含水量，而這項指標與其他物理性質有明顯的相關性。先前實驗室訂定了測量細菌纖維素含水量的準則(藍翊蓁，2017)，可以客觀地呈現含水量的數值。隨後的另一項研究(范千鈺，2020)，利用不同碳源和培養環境，生長出不同產量和含水量的細菌纖維素，並發現兩者呈現反向關係。 本研究探討細菌纖維素浸泡3.125 × 10-7 M硫酸鎂水溶液後，其電阻率與含水量之關係，研究結果顯示當含水量為224.9 ± 16.3 (g H2O/g dry BC)時，其電阻率約為107.4 ± 6.1 (Ω-m)；而含水量為56.3 ± 2.2 (g H2O/g dry BC)時，其電阻率則約為297.3 ± 47.7 (Ω-m)，兩者呈現一反向關係，這可能與細菌纖維素結構的緊密程度有關，因而影響離子在細菌纖維素內部的流動性。 另一方面，由於肉眼即能觀察到細菌纖維素的透光程度與含水量有相關，故本研究以650 nm作為測量波長，來探討細菌纖維素的透光率，以此做為定量細菌纖維素透光程度的指標。研究結果發現當含水量為221.9 ± 12.7 (g H2O/g dry BC)時，其透光率約為43.8 ± 3.7 (%)；而含水量為56.3 ± 2.2 (g H2O/g dry BC)時，其透光率則約為7.3 ± 1.3 (%)，兩者呈現正向關係，同樣地，這可能與細菌纖維素結構的緊密程度有關，因而影響光線穿透細菌纖維素。 關鍵字：細菌纖維素、含水量、電阻率、透光率

Bacterial cellulose (BC) is a 3D nano-network structure polymer made from glucose monomers, and therefore contains many hydrophilic hydroxyl groups on its chain, giving it a high water holding capacity (WHC). This indicator, WHC, is significantly correlated with other physical properties. Our lab previously established a criterion for measuring the WHC of BC (Lan, 2017), objectively and successfully related BC yields grown by different carbon sources and WHC (Fan, 2020). In this study, the relationship between the electrical resistivity and WHC of BC soaked in a 3.125 × 10-7 M MgSO4 aqueous solution was investigated. The results showed that the electrical resistivity was approximately 107.4 ± 6.1 (Ω-m) when the WHC was about 224.9 ± 16.3 (g H2O/g dry BC). In contrast, the electrical resistivity was approximately 297.3 ± 47.7 (Ω-m) when the WHC was about 56.3 ± 2.2 (g H2O/g dry BC). An inverse relationship was confirmed that may be due to the compactness of the BC structure and the mobility of ions within the BC. On the other hand, because the transparency of BC was noticed. The WHC was further positively related to the transmittance at 650 nm. The results showed that when the WHC was about 221.9 ± 12.7 (g H2O/g dry BC), the transmittance was approximately 43.8 ± 3.7 (%), while at a WHC of 56.3 ± 2.2 (g H2O/g dry BC), the transmittance was around 7.3 ± 1.3 (%). This phenomenon may be due to the tightness of the BC structure, as light may be blocked by the cellulose fibers. Keywords: bacterial cellulose, water holding capacity, electrical resistivity, transmittance