Preparation process of bacterial cellulose

Bacterial Cellulose (BC) is a cellulose material synthesized by bacteria. It has high purity, high crystallinity, high mechanical strength and other characteristics. It is widely used in biomedicine, food, environmental protection and other fields. The following is the preparation process for bacterial cellulose:

1. Preparation process of bacterial cellulose

1. Select bacterial strains
to prepare bacterial cellulose The most commonly used strain is Gluconacetobacter xylinus of the genus genus Gluconacetobacter xylinus because it can synthesize cellulose efficiently. In addition, other bacterial species with cellulose-producing power can also be used to prepare bacterial cellulose.

2. Preparation of culture medium The synthesis of
bacterial cellulose requires rich nutrients. Commonly used culture medium include HS culture medium (Hestrin-Schramm culture medium), and its main components are:

oGlucose : As a carbon source, bacteria metabolize to produce cellulose.

o Peptone and yeast extract: Provides nitrogen source and growth factors.

oSodium hydrogen phosphate dihydrate and citric acid: adjust the pH value of the culture medium.

The specific formulation of the culture medium may be adjusted according to the needs of experimental design or industrial production.

3. Sterilization
The prepared culture medium is subjected to high-temperature autoclave, usually sterilized at 121°C for 15-20 minutes to ensure that the culture medium is sterile and avoid contamination of bacteria.

4. Inoculate bacteria.
Purified bacteria are inoculated into the sterilized culture medium. Common inoculation methods include liquid culture and solid culture. Liquid culture is often used in laboratory production, while solid culture (such as inoculation on solid surfaces) is often used in industrial production to form bacterial cellulose membranes with a certain thickness.

5. Stand fermentation
The inoculated culture medium is allowed to stand under constant temperature conditions. The common temperature range is 28-30℃ and the culture time is 7-14 days. The specific time depends on the requirements of cellulose yield and thickness. Bacteria grow on the static fluid surface, secrete cellulose to form a gel-like membrane, which gradually thickens.

6. After the fermentation of the cellulose membrane
is completed, carefully remove the bacterial cellulose membrane (also known as BC membrane) on the surface of the culture medium with a sterile tool. The cellulose film at this time contains a lot of moisture and is gel-like.

7. Purification and treatment
The bacterial cellulose membrane may contain impurities such as bacterial residues, culture medium components, and purification treatment is required. A commonly used purification method is to heat and boil the cellulose membrane in 0.1 M NaOH solution for 1-2 hours, remove impurities, and then rinse repeatedly with a large amount of deionized water until the pH value is close to neutral.

8. Dry or store
purified bacterial cellulose can be processed according to the purpose:

oDrying : The cellulose can be dehydrated and dried by freeze-drying, hot air drying, etc. to obtain a dried bacterial cellulose film or powder for subsequent applications.

o Wet storage : If you need to maintain the hydrogel state of bacterial cellulose, you can store it in sterile water or buffer to maintain its moisture content and flexibility for easy subsequent use.

2. Factors affecting bacterial cellulose yield

1. Culture medium formula : The proportion of carbon source, nitrogen source, and trace elements will significantly affect the yield and quality of cellulose. Optimizing the culture medium formula is an important means to increase yield.

2. Fermentation conditions : Conditions such as temperature, pH, and ventilation have an important impact on the metabolic activity of bacteria and the formation of cellulose. Production is usually optimized by adjusting the fermentation conditions.

3. Strain selection and improvement : Different strains have different cellulose-producing abilities, and yield and quality can be improved through strain screening or genetic engineering.

III. Application prospects of bacterial cellulose

Because bacterial cellulose has high strength, high purity, good biocompatibility and other characteristics, it is in biomedical science (such as artificial skin, tissue engineering), food industry (such as thickeners, low-calorie dietary fiber), and environmental protection (such as water) There is great potential for application in fields such as processing membrane materials.

With the optimization of process and technological progress, the production cost of bacterial cellulose is gradually reduced, and the application prospects in various industries will be broader in the future.