Bacterial Cellulose Spheres that Encapsulate Solid Materials

Summary

This protocol presents an easy, inexpensive method of forming bacterial cellulose (BC) spheres. This biomaterial can function as an encapsulation medium for solid materials, including biochar, polymer spheres, and mine waste.

Abstract

Bacterial cellulose (BC) spheres have been increasingly researched since the popularization of BC as a novel material. This protocol presents an affordable and simple method for BC sphere production. In addition to producing these spheres, an encapsulation method for solid particles has also been identified. To produce BC spheres, water, black tea, sugar, vinegar, and bacterial culture are combined in a baffled flask and the contents are agitated. After determining the proper culture conditions for BC sphere formation, their ability to encapsulate solid particles was tested using biochar, polymer beads, and mine waste. Spheres were characterized using ImageJ software and thermal gravimetric analysis (TGA). Results indicate that spheres with 7.5 mm diameters can be made in 7 days. Adding various particles increases the average size range of the BC capsules. The spheres encapsulated 10 - 20% of their dry mass. This method shows low-cost sphere production and encapsulation that is possible with easily obtainable materials. BC spheres may be used in the future as a contaminant removal aid, controlled release fertilizer coating, or soil amendment.

Introduction

Bacterial cellulose (BC) has been noted for its potential industry use due to its mechanical strength, high purity and crystallinity, water retention abilities, and intricate fiber structure^1,2,3,4. These characteristics make BC a favorable biomaterial for a variety of applications, including biomedical, food processing, and environmental remediation uses¹. Formation of a BC film can be done with single organism cultures or mixed cultures like those used for kombucha⁵, a fermented tea beverage.....

Protocol

1. Creation and maintenance of bacterial cellulose starter culture

1. Obtain a starter culture of bacterial cellulose, approximately 50 g, in the form of a SCOBY. It can be purchased commercially (e.g., from Cultures for Health). Place the SCOBY into a 1 L beaker, covered with a paper towel.
2. Boil 700 mL of deionized water, transfer it to a separate vessel from the one containing the SCOBY, and add 85 g of sucrose.
3. Once the sucrose has dissolved, add 2 bags of black tea (4.87 g). Steep the tea for 1 h, then carefully remove the tea bags using a stir rod.
4. Add 200 mL of distilled white vinegar to the tea. Let the mixture cool to 25 ....

Results

BC spheres have the fastest growth rate during the first 48 h of culture (Figure 2). Figure 2 also shows how the spheres tend to reach a maximum average size and then remain constant. In this experiment, the spheres reached an average diameter of 7.5 ± 0.2 mm. Although the BC spheres never completely deteriorate within the 10 day growth period, they did start to form tendrils that extend off the main body of the sphere around the eighth day. This can be see.......

Discussion

This protocol outlines BC sphere production and encapsulation methods that are easy to conduct and cost effective. Through various adjustments to the original protocol, an adequate process has been identified. Critical steps must be followed to ensure viable spheres. All the ingredients involved in BC formation play a key role in the health and durability of the spheres. The sucrose feeds organisms, the tea provides nitrogen, and the vinegar lowers the pH to optimal conditions to prevent undesired contaminants

Materials

Name	Company	Catalog Number	Comments
100 mL graduated cylinder
1000 mL beaker
25 mL graduated cylinder
250 mL Erlenmeyer baffled flask	Chemglass	CLS-2040-02
500 mL beaker
Balance
Biochar			Ponderosa pine heat treated under argon gas, heated at 15 °C per minute to 800 °C
Black tea
Deionized water
Distilled white vinegar
Elastic band
Microbial starter culture	Cultures for Health
Mine waste			Collected from Butte, MT: 46.001978,-112.582465. Mine waste contains soil and metals originating from past copper mining. Mn, Si, Ca, Al, and Fe were the five most prevalent elements measured in the mine waste through x-ray diffraction.
Mortar and pestle
Orbital shaker			Used various brands
Paper towel
Polystyrene microbeads	Polybead	17138	3 micron diameter
Stir rod
Sucrose
Tea kettle
TGA	TA Instruments	TA Q500	400 °C/min to 800 °C, 100 mL/min N2
Thermometer
XRF Analyzer	ThermoFisher Scientific	10131166