Spray-dried redispersible bacterial nanocellulose microspheres

ROSAS MD; CERRUTTI P; BUCALÁ V; RAMÍREZ RIGO MV; FORESTI ML

Porto

Congreso; 4th INTERNATIONAL SYMPOSIUM ON BACTERIAL NANOCELLULOSE; 2019

University of Minho

The economic and technical disadvantages associated with the wet storage and transport of nanocelluloses trigger the development of simple methods able to produce nano-scaled cellulose products with lower water content (1). However, the irreversible aggregation of cellulose nanofibrils during dehydration (hornification) still poses a problem for the production of dried nanofibrillated celluloses. In this context, different alternatives have been proposed to produce redispersible nanofibrillated cellulose (mainly from vegetal origin), including chemical modification and the incorporation of additives during drying that can hinder hydrogen bond formation among cellulose nanofibers. With this aim, additives such as sodium chloride (2), carboxymethyl cellulose (3), cetyltrimethylammonium bromide (4), poly (vinyl-alcohol) (1), and maltodextrin (5), have been used. In the current contribution, bacterial nanocellulose (BNC) microspheres were produced by spray drying of a BNC aqueous suspension using mannitol as drying adjuvant. The feed properties and operating conditions (i.e. BNC suspension solid content, mannitol:BNC ratio, air inlet temperature, atomization air flow rate, drying air flow rate and liquid feed flow rate), were all adjusted to obtain a powdered product with a yield of 78 wt%. Scanning electron microscopy images of the recovered powder evidenced the obtention of sphere-shaped particles with diameters not higher than 10 m. Particle size distribution (PSD) results obtained by laser diffraction further indicated a unimodal and narrow PSD as the span value obtained was 1,03. The mean volumetric diameter of the particles was 6,36 ± 0,11 μm. Besides, 10, 50 and 90 wt% of the particles exhibited diameters below 3,58 ± 0,03 μm, 5,91 ± 0,08 μm and 9,67 ± 0,21 μm, respectively (results from three replicates).The spray-dried BNC microspheres were evaluated in terms of their redispersibility in water upon magnetic stirring and ultrasonication. Results indicated that whereas in magnetically stirred aqueous suspensions BNC spheres showed some deformation but still retained their integrity, mild ultrasonication during short periods of time (5-15 min) caused BNC microspheres to break down into loose BNC nanofibers. The BNC microspheres obtained using mannitol, a naturally occurring sugar alcohol widely used in food and medical applications, have a vast potential for redispersible BNC production.