Methods for biological preparation of nanofibers

Nanofibers are an important nanomaterial and have attracted much attention due to their high specific surface area, excellent mechanical properties and wide application potential. The preparation of nanofibers by biological methods has the advantages of green environmental protection, low energy consumption and high controllability. Natural resources and biotechnology such as microorganisms, plants or biological enzymes are often used to achieve the preparation of nanofibers. The following is a detailed introduction from the methods, principles and specific steps.

1. The main methods for biological preparation of nanofibers

1. Preparation of bacterial cellulose

Bacterial Cellulose (BC) is a nanofiber material produced by specific bacteria, such as Cellulose, through biosynthetic pathways.

Principle: Bacteria convert carbon sources such as glucose into bacterial cellulose and secrete them into the culture medium in the form of nanofibers.

Advantages: The fiber has high purity, uniform size, excellent mechanical properties, and is suitable for direct use or further processing.

Preparation steps:

Strain culture: Inoculate strains of Acetobacter xylinum into culture medium, which usually contains glucose, peptone, and yeast extract.

Fermentation: Cultivate bacteria under static or shaking conditions, and bacteria secrete cellulose to form a three-dimensional nanofiber network, which usually takes 5-10 days.

Collect and purification: Collect cellulose membranes on the surface of the culture medium and treat them with lye (such as NaOH) to remove bacterial and protein impurities.

Washing and drying: The cellulose membrane is repeatedly washed with deionized water until neutral, and then freeze-dried or heat-dried to obtain bacterial cellulose nanofibers.

2. Plant fiber deconstruction method

Using plant fibers (such as wood, cotton, sugar cane bagasse, etc.) as raw materials, it is deconstructed into through biotechnology.nanocellulose 。

Preparation method:

principle:

Plant cellulose is a composite structure composed of cellulose microfibers, lignin and hemicellulose.

Non-cellulose components are degraded through biological enzymatic lysis, microbial fermentation and other means, and the cellulose is decomposed into nano-scale microfiber filaments.

step:

Raw material treatment: Pretreat the plant fibers (such as mechanical crushing or steam blasting) to increase the fiber surface area and reduce lignin content.

Enzymatic treatment: Add cellulase or hemicellulase to hydrolyze the pretreated plant fibers to release nanocellulose。

Centrifugation and purification: The cellulose microfiber filaments are separated by high-speed centrifugation, washed and removed impurities.

Dry: Freeze-drying or spray-drying to obtain the final nanocellulose.

3. Bioenzyme catalysis method

Use specific enzymes, such as cellulase, to degrade plant fibers, selectively remove lignin and hemicellulose, thereby obtaining nanofibers.

principle:

Biological enzymes are highly catalytically specific and can decompose cellulose raw materials under mild conditions, avoiding common contamination and high energy consumption problems in chemical methods.

Preparation steps:

Select enzyme species: Select cellulase or complex enzyme with high activity, which can efficiently decompose cellulose into nano-scale fibers.

Enzymatic reaction: React plant fibers with cellulase at specific temperatures and pH, and the reaction time is usually 24-72 hours.

Separation and purification: Removal by-products and excess enzyme solution by centrifugation and water washing to obtain a pure nanocellulose suspension.

Drying treatment: freeze-drying or spray-drying to obtain powdered or film-like nanocellulose。

2. Advantages of preparation of nanofibers by biological methods

Green and environmental protection: biological methods rely on the action of microorganisms or enzymes, avoid the use of harmful chemical reagents such as strong acids and strong alkalis, and reduce pollution.

Low energy consumption: mild reaction conditions (conditional temperature or medium-low temperature), and the energy consumption is lower than that of chemical methods.

High Purity Products: Nanofibers prepared by biological pathways are usually of high purity without additional chemical purification steps.

Renewable resource utilization: Make full use of natural resources (such as agricultural and forestry waste) to prepare high value-added nanofiber materials.

III. Application of biological preparation of nanofibers

Reinforced composite materials: Nanofiber reinforced polymer composite materials, used in lightweight structural materials, automotive parts and other fields.

Green packaging: used for high barrier biodegradable packaging materials, replacing traditional plastics.

Medical field: As a drug carrier, tissue engineering stent, etc., it has good biocompatibility.

Filtration Materials: Nanofibers can be used in air filtration and water treatment, demonstrating excellent filtration efficiency and sustainability.

The preparation of nanofibers in biological methods has become an important means for preparing high-performance nanomaterials due to their environmentally friendly, economical and efficient characteristics. Through bacterial synthesis, plant deconstruction and enzyme catalysis, different types of nanocellulose can be obtained to meet the diverse needs of composite materials, packaging, medical care and other fields, etc.