Structural investigations of microbial cellulose produced in stationary and agitated culture

Structural characteristics of microbial cellulose synthesized by two different methods have been compared using FT-IR and X-ray diffraction techniques. Cellulose synthesized by Acetobacter xylinum NQ-5 strain from agitated culture conditions is characterized by a lower Ia mass fraction than cellulose that was produced statically. Such a decrease was in good correlation with smaller crystallite sizes of microfibrils produced in agitated culture. Formation of characteristic cellulose spheres during agitation has been investigated by various electron and light microscopic methods. On this basis, a hypothetical mechanism of sphere formation and cell arrangement in the agitated culture has been proposed. During agitation, cells are stacked together in organized groups around the outer surface of the cellulose sphere. Introduction cellulose include: an acoustic transducer dia­ phragm made of dried cellulose sheet (Nishi Cellulose is the most abundant biopolymer on et al. 1990), wound dressing material (artificial earth and is produced by a variety of organ­ skin) made of wet and purified cellulosic mem­ isms, ranging from vascular plants to algae and brane (Fontana et al. 1990), or Nata de Coco, a prokaryotic organisms such as cyanobacteria traditional Philippine fermented dessert, which (Jonas and Farah 1998; Nobles et al. 2001). In became very popular in Japan a few years ago addition, there are some strains of the (Yoshinaga et al. 1997). In recent years, an prokaryotic, non-photosynthetic organism, Ace­ interest has developed in producing bacterial tobacter, which have the ability to synthesize cellulose on a large commercial scale. Some at­ high-quality cellulose organized as twisting rib­ tempts have been made in the area of optimi­ bons of microfibril bundles (Brown et al. 1992). zation of culture conditions (Kouda et al. 1997a, Bacterial cellulose demonstrates unique proper­ b), medium composition (Matsuoka et al. 1996), ties including high mechanical strength, high strain improvement (Ishikawa et al. 1995; crystallinity, high water holding capacity and Vandamme et al. 1998), or the scaling-up pro­ high porosity, which make it a very useful bio­ cess, but few production yield enhancements material in many different industrial processes have been reported so far. (Brown 1998; Iguchi et al. 2000). So far, the There are two methods to produce bacterial best-known commercial applications of bacterial cellulose: (a) stationary culture, which results in