In fungal fermentation for producing alcohol, vinegar, soy sauce, or miso, waste like liquor meal or distillers’ grains is generated. Researchers have repurposed beer spent grain (BSG) to extract proteins, modifying their properties for potential use as wood adhesives. This study utilized six fungal materials to produce protein adhesives via centrifugation, alkali hydrolysis, acid neutralization, and centrifugal concentration. The most promising results in small-scale adhesive tests came from protein extracted from red yeast (Monascus purpureus) and koji rice bacteria (Aspergillus oryzae).
Adhesive properties of wood panels were evaluated using the CNS National Standard of the Republic of China, at the Taiwan Testing and Certification Center (ETC).
A complex of red yeast protein (Monascus purpureus protein, MPP) and tannic acid (TA) exhibited enhanced properties, including antibacterial and waterproof abilities, along with increased bonding strength, evidenced by a 15mm inhibitory zone.
The compressive load method shows:
Tannic acid was added to red yeast rice protein to improve its properties and enhance the strength of fungal protein-based adhesive. Statistical results showed differences.
Despite having good adhesion results, red yeast protein (Monascus purpureus protein, MPP) extraction rate is only 0.8%. The extraction steps of fungal proteins must be optimized, such as the concentration of alkali lysis or the temperature and time of heating, etc., to increase the yield and reduce costs.
Red yeast protein (MPP) glue has the best test results in the tensile load method. The data shows that it can reach 2 times the shear strength of commercially available white glue. In future mass production, the extraction steps of red yeast protein (MPP) need to be optimized, such as alkali concentration or the temperature and time of heating, etc., can increase the yield and reduce the cost.
The optimal ratio of red yeast protein (MPP) and tannic acid (TA) to form a complex is 1:2, which can increase the complex production by 11.1%. Centrifuge and absorb the supernatant and place the precipitated complex on filter paper. The moisture content obtained after drying the water is 10.39%.
The total strength of the purified red yeast protein adhesive could hold up to 450 kg of wood when stress was applied. However, the effects of the adhesive on steel and acrylic pieces were not as effective.
Interpretation of antibacterial activity is based on the average value obtained by measuring the diameter of the inhibitory zone. A diameter greater than 10.0 mm indicates antibacterial activity, 10.0 mm indicates mild activity, 11.0–15.0 mm indicates moderate activity, and 16.0–20.0 mm indicates antibacterial activity. Only tannic acid has a high inhibitory effect on the growth of Escherichia coli, with an average inhibition zone diameter of 20.0 mm. The red yeast protein + tannic acid (MPP-TA) group has a moderate inhibitory effect on the growth of Escherichia coli, with an average inhibition zone diameter of 15.0 mm. Use the complex formed by mixing red yeast protein and tannic acid as glue, then measure the shear force.
The results of the compressive load method show that the shear strength of the glue is the control group (white glue). The results of the tensile load method show that the shear strength of the adhesive is 271.3% of the control group (commercial white glue).
Statistical method t testa results show that there is a significant difference P ‹ 0.05 in the shear resistance of red yeast protein and tannic acid viscose and commercial white glue in the compressive loading method and tensile loading method. There is a significant difference of P ‹ 0.001.
In the reference literature, the protein extracted from beer lees is added to other compounds to improve its properties. We can also try to adjust the pH value of the fungal protein glue, or add thickeners, coagulants, etc. to improve our adhesive.
MPP-TA is also the first ever complex to be developed and extended into a paper; there exists no other material or research regarding the combination of Monascus purpureus and Tannic Acid, and by the looks of these significant results, deserves to be continued and developed in strengthening the superglue and other properties.
The production process of conventional plant protein adhesives often consumes a significant amount of water and energy, leading to potential waste and increased emissions of pollutants, and carbon dioxide emissions. By using by-products of fungal fermentation or brewing to produce protein glue, it’s possible to reduce the consumption of natural resources, decrease environmental impact, and create new products to increase value. In the future, fungal protein adhesives can provide a natural and non-toxic choice for wood bonding.
Furthermore, after confirming the adhesive properties of red yeast protein glue, we can conduct additional tests to further characterize the properties of this adhesive, including:
This experiment has confirmed the high feasibility of using extracted red yeast protein (Monascus purpureus protein, MPP) as a natural and efficient adhesive, the first ever complex made regarding these two substances. It has been proven to have properties that are worth developing and strengthening, such as superglue strength, antibacterial, and waterproof abilities.
Tannic acid, a common hydrolysable tannin, also absorbs chitosan, an alkaline substance found mostly in the exoskeleton of crustaceans. It is common for this compound to also react with different organic compounds, such as arginine, polyamines, chitin, and chitosan. This opens new possibilities for various industries.
Traditional protein adhesive preparation processes often involve significant water and energy consumption and may result in waste and emissions. Utilizing MPP-TA to produce protein adhesives holds the promise of reducing reliance on natural resources and minimizing environmental impact.
Additives: Used to improve the dyeing, printing, and texture of fibers to produce biodegradable textiles.
Fungal protein adhesives can be used as drug delivery systems to enhance drug stability and delivery efficiency.
Fungal protein adhesives can be used in medical devices such as surgical sutures and biodegradable implants, helping to improve biocompatibility and reduce allergic reactions.
Structural Materials: Fungal protein adhesives can be used to produce bio-based construction materials, including walls, panels, and structural materials.
Structural Materials: Fungal protein adhesives can be used to produce bio-based construction materials, including walls, panels, and structural materials.
Biodegradable Packaging: Fungal protein adhesives can be used to create biodegradable packaging materials, reducing issues related to plastic waste.
Biodegradable Packaging: Fungal protein adhesives can be used to create biodegradable packaging materials, reducing issues related to plastic waste.
