Production and characterization of nanospheres of bacterial cellulose from Acetobacter xylinum from processed rice bark F.D.E. Goelzer a , P.C.S. Faria-Tischer a,b , J.C. Vitorino a , Maria -R. Sierakowski b , C.A. Tischer a, ⁎ a Group of Industrial Microbiology, UNIVALI-Universidade do Vale do Itajaí, R. Uruguai, 458, 88302-202, Itajaí, Santa Catarina, Brazil b Laboratory of Biopolymers, UFPR-Universidade Federal do Paraná, CxP 19081, 81531-990, Curitiba, Paraná, Brazil abstract article info Article history: Received 31 May 2008 Received in revised form 30 September 2008 Accepted 2 October 2008 Available online 18 October 2008 Keywords: Cellulose Nanostructure Acetobacter xylinum Atomic force microscopy X-ray diffraction Bacterial cellulose (BC), biosynthesized by Acetobacter xylinum, was produced in a medium consisting of rice bark pre-treated with an enzymatic pool. Rice bark was evaluated as a carbon source by complete enzymatic hydrolysis and monosaccharide composition (GC-MS of derived alditol acetates). It was treated enzymatically and then enriched with glucose up to 4% (w/v). The BC produced by static and aerated processes was purified by immersion in 0.1 M NaOH, was characterized by FT-IR, X-ray diffraction and the biosynthetic nanostructures were evaluated by Scanning Electronic (SEM), Transmission Electronic (TEM) and Atomic Force Microscopy (AFM). The BC films arising from static fermentation with rice bark/glucose and glucose are tightly intertwined, partially crystalline, being type II cellulose produced with rice bark/glucose, and type I to the produced in a glucose medium. The nanostructurated biopolymer obtained from the rice bark/glucose medium, produced in a reactor with air flux had micro- and nanospheres linked to nanofibers of cellulose. These results indicate that the bark components, namely lignins, hemicelluloses or mineral contents, interact with the cellulose forming micro- and nanostructures with potential use to incorporate drugs. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Bacterial cellulose (BC) is one of the most promising biomaterial nanostructured, displaying unique properties with a broad perspective for application in different fields, including composite membranes, medicine, artificial skins, blood vessels, and binding agents [1–5]. There are some microorganisms capable of synthesizing cellulose, but Acetobacter xylinum is the only one that can form it in sufficient abundance for industrial application [6]. The gram-negative bacteria, reclassified in 1997 as Gluconoacetobacter xylinus [7], synthesises a network nanostructurated formed by cellulose fibers with high mechan- ical resistance, as a result of their physical and chemical arrangement. This biosynthesis occurs via the enzymatic complex of cellulose synthetase that is associated with the pores on the surface of the bacillus [8]. Certain characteristics of bacterial cellulose are unique, making it a very interesting polymer with several commercial applications. It is free of lignin and hemicelluloses, and can be isolated pure without further treatment, distinguishing it from those obtained from plants. It has a higher degree of crystallinity, swelling capacity and degree of polymer- ization, making it an economically important alternative, with properties originating from its ultra-fine reticulated nanostructure [9,10]. Cellulose with different morphological characteristics can be obtained using different methods of culture, namely static, submerged or agitated. Variations in the composition of the culture medium, agitation and aeration give rise to aggregates of microfibrils with different forms [11,12]. The production of bacterial cellulose on static culture is the most inexpensive and easiest process, since under this condition; the bacillus produces cellulose at the air/liquid interface. The diameter of the microfibrils is less than 50 nm; they turn forming macrofibrils with diameter in the micrometer range [13] that together represents the construction units of the cellulose fiber, which is characterized by layers differing in fibril texture. Bacterial cellulose produced in agitated medium does not produce films of cellulose, rather than irregular granules dispersed throughout the medium [14]. Different sources of carbon can be used by A. xylinum to produce cellulose [8,15] and investigations have been carried out to find alternative substrates with low cost and capable to avoid or reduce environmental damage. The use of agricultural residues, as rice bark, is one interesting alternative. In the southern region of Brazil, particularly in the State of Santa Catarina, occupies the second position in national rice production with 1.071.559 tons, representing 13.3% of production [16], rice bark is a biproduct obtained after treatment of the grain and represents 23% of its dry weight. This agricultural residue contains ~570 g/kg of total carbohydrates as cellulose, hemicelluloses [17], addition of metallic ions, such as sodium, calcium, potassium, iron, aluminium and mag- nesium [18,19], that are actually burned as fuel in furnaces. The great interest in bacterial cellulose arises from its specific structure, composed of repeating glucose residues, that generates diverse architectures. Variation of culture conditions and sources of carbon can Materials Science and Engineering C 29 (2009) 546–551 ⁎ Corresponding author. Rua Uruguai, 458, bloco 17, sala 312, Itajaí-SC, 88302-202, Brazil. Tel.: +55 47 33417500r.8123. E-mail address: cesarat@uol.com.br (C.A. Tischer). 0928-4931/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.msec.2008.10.013 Contents lists available at ScienceDirect Materials Science and Engineering C journal homepage: www.elsevier.com/locate/msec