Fluidized-Bed Granulation of Probiotics-Encapsulated Spray-Dried Skim Milk Powder: Effects of a Fluidizing Aid, Moisture-Activation and Dehydration.

A probiotic powder of poor flowability with high dust content, prepared by spray drying reconstituted skim milk fermented with Lactobacillus rhamnosus GG (LGG), was granulated by fluidized-bed granulation (FBG). The effects of the addition of skim milk powder (SMP) as a fluidizing aid, and of simple moisture-activation with or without dehydration, were investigated with respect to the performance of the FBG process. A fine, poorly fluidizable LGG powder (Geldart Group C) could be fluidized and granulated, with a 4- to 5-fold increase in particle size (d4,3 = 96-141 µm), by mixing with SMP (30-50%), which has larger, fluidizable particles belonging to Geldart Group A. Moisture-activation after the mixing, followed by fluidized-bed dehydration with hot air to remove excess moisture, further improved the FBG; the yield of the granules increased from 42% to 61% and the particle size distribution became much narrower, although the average particle size remained almost the same (d4,3 = 142 µm). These granules showed a popcorn-type structure in scanning electron microscopy images and encapsulated a sufficient level of viable LGG cells (1.6 × 108 CFU g-1). These granules also exhibited much better flowability and dispersibility than the spray-dried LGG powder.

Symbiotic culture of nanocellulose pellicle: A potential matrix for 3D bioprinting.

Nanocellulose pellicle is produced as a byproduct during the symbiotic culture of bacteria and yeast in kombucha. It shows good mechanical strength, biocompatibility and hydrophilicity. However, it has limited application in tissue engineering due to its low processability. In this work, bacterial cellulose-based sustainable kombucha (KBC) sheet has been produced and it was acid-treated to partially hydrolyse. This controlled process improves its extrusion and shape formation ability. The physical, functional and biological properties were studied to assess its potential as a 3D printed scaffold. Two different cell lines (Human dermal fibroblast cells and mouse osteoblast cells) were used to study the cytocompatibility. Both the cell types showed good attachment, growth and proliferation on the pure and treated KBC. They attained almost full confluence within 3 days. This study indicates that the controlled partial hydrolysis of KBC can make it suitable for 3D printing retaining its mechanical strength and cytocompatibility. This sustainable microbial biopolymer shows the possibility to be used as a bioink for 3D bioprinting.