Assessment of the Gastrointestinal Fate of Bacterial Cellulose and Its Toxicological Effects After Repeated-dose Oral Administration

BackgroundBacterial cellulose (BC) is a nanofibrillar polysaccharide produced by certain acetic acid bacteria. BC may be used in food, pharma and many other applications. However, detailed studies of the oral toxicology of BC are limited. Controversial data is published regarding this topic, specially when it comes to answering the question on whether cellulose is absorbed at the intestine.MethodsFollowing the European Food Safety Authority guidelines (EFSA), this work presents the results of a 21-day repeated dose oral toxicity of BC in male and female Wistar Han rats (Wistar rats). In parallel, microcrystalline cellulose Avicel LM310 (commercially available as a food additive) was used. Wistar rats were subjected to daily oral gavage of 0.75 mL of an aqueous suspension 1% (m/v) BC or of its counterpart of plant origin, Avicel LM310. Rats not submitted to gavage were included in the experiment as controls. Clinical observations, such as body weight measurements, food consumption and ophthalmologic evaluations were performed during the assay. After occision, serum chemistry, necropsic examination and histopathological analyses of the liver, kidneys, spleen and small and large intestines were performed. The presence of BC fibers along the gastrointestinal tract was assessed histologically using a Green Fluorescence Protein coupled to a Cellulose Carbohydrate Binding Module (GFP-CBM) from Clostridium cellulolyticum.ResultsNo adverse clinical observations related to BC administration were noticed, nor appreciable differences in the toxicological endpoints evaluated were detected. No evidence of BC persorption was found. Particularly, no BC was detected in the Peyer´s patches or in the mesenteric lymphatic nodules. Moreover, the histopathological analyses revealed that the global architecture and morphology of the organs and tissues was preserved, among the different experimental groups, with no significant pathological changes among them. Regarding serum biochemistry, no significant differences were recorded, for both sexes.ConclusionsThese results demonstrate that BC nanofibers can be considered safe and, as the vegetal cellulose, can be used as a food additive.