Sericin: Turning Waste into Wealth – Exploring Innovative Applications for a Sustainable Future

Amrit Layak* 

*Scientist B, Central Silk Board, Regional Silk Technological Research Station, Varanasi, Uttar Pradesh, India

Abstract

This article delves into the extraction, chemical composition, and multifaceted applications of sericin, a by-product of the silk industry. Despite being a historically neglected biopolymer, sericin has recently gained attention for its eco-friendly, biodegradable properties, making it valuable in cosmetics, pharmaceuticals, nutraceuticals, and biomedical applications. Apart from these application areas, the current article compiles findings from recent studies, emphasising sericin’s potential in drug delivery, tissue engineering, and medical textiles.

1. Introduction

Sericin, a protein extracted from silk, constitutes 20-30% of silk protein and is primarily discarded as waste in silk production. During the silk production process, a significant portion of sericin is typically lost in the degumming and reeling water. Since sericin is the second largest component of raw silk (after fibroin), it is estimated that out of 400,000 tons of dry cocoons produced worldwide, 50,000 tons of sericin are (usually) discarded in the effluent causing environmental problems. (Aramwit et al., 2012 ; Giacomin et al., 2017 ; Lu et al., 2022). This occurs as sericin, which coats the silk fibroin fibres, is removed to produce lustrous silk threads. These losses present an underutilised opportunity, as the discarded sericin is rich in bioactive properties, making it valuable for various applications in cosmetics, pharmaceuticals, and biotechnology. Targeting the recovery of sericin from degumming and reeling water provides an eco-friendly source of this biopolymer while also reducing waste and valorizing it in the silk industry value chain. Chemically, sericin contains 18 amino acids, including serine (32%), glycine (19%), aspartic acid (16%), and alanine (11%). These characteristics make sericin a versatile material for various applications due to its film-forming, moisture-retaining, and biodegradable properties. (Rangi et.al., 2015). 

From an economic point of view, the extraction of sericin from degumming water aligns with the principles of circular economy and waste valorization. By transforming waste into a high-value product, silk producers can diversify their income streams. Sericin’s application in cosmetics is a rapidly growing segment. The global skin care products market size was estimated at USD 135.83 billion in 2022 and is projected to grow at a compound annual growth rate (CAGR) of 4.7% from 2023 to 2030. Escalating demand for face creams, sunscreens, and body lotions across the globe is expected to positively impact the growth. The pharmaceutical sector, particularly in drug delivery and wound care, has seen increasing demand for sericin-based hydrogels and films due to their controlled release properties. The global biomaterials market size was estimated at USD 178.0 billion in 2023 and is projected to grow at a CAGR of 15.6% from 2024 to 2030. Sericin’s antioxidant properties also have applications in the nutraceutical market and the global nutraceuticals market size was valued at USD 712.97 billion in 2023 and is expected to grow at a CAGR of 8.4% from 2024 to 2030. (Grand View Research). While talking about the global scenario, India is actively advancing in the sericin market. As of 2024, the Indian sericin market had a valuation of USD 11.38 million and is expected to grow at a compound annual growth rate (CAGR) of 9.8% during the forecast period. This growth is driven by increasing demand for natural and sustainable ingredients, particularly in industries like cosmetics and pharmaceuticals, reflecting India’s commitment to leveraging eco-friendly materials and bio-based products. (Cognitive Market Research).

2. Sericin Extraction Methods

Various methods of sericin extraction are as follows: 

1. Alkali Extraction: Involves the use of sodium carbonate or other alkaline agents. It efficiently separates sericin from fibroin but poses environmental concerns (Kundu et al., 2008).
2. Heat-Based Extraction: A simpler method that relies on boiling silk. While cost-effective, this method may denature sericin proteins, affecting its functional properties.
3. Enzymatic Extraction: Eco-friendly and preserves sericin’s bioactivity by using proteolytic enzymes to break the bonds between sericin and fibroin (Orlandi et al., 2021).
4. Membrane Dialysis: A novel technique that separates sericin from degumming wastewater through selective membranes, minimising the use of harsh chemicals (Silva et al., 2022).

Table 1. Various methods for sericin extraction, highlighting their respective advantages, and limitations (Silva et al., 2022)

Extraction Method	Approach	Advantages	Limitations
Conventional	Detergents/soaps (e.g., Marseille) and sodium bicarbonate	Effective	Sericin is significantly degraded; recovery is difficult; not eco-friendly due to effluent issues
Chemical
– Alkaline Solutions	Sodium carbonate, phosphate, silicate, hydrosulphite	Fast, low-cost, efficient	Causes sericin degradation; difficult to recover; requires purification; environmentally problematic
– Acidic Solutions	Citric, tartaric, succinic acids	Less degradation compared to alkaline solutions	Still results in sericin degradation; not efficient; needs purification; not eco-friendly
– Urea-Based	Urea, with or without mercaptoethanol	Effective in extraction; minimal sericin degradation	Time-consuming; requires purification to remove chemical residues; potential cell toxicity
Enzymatic	Proteolytic enzymes (e.g., bromelain, pancreatin, alcalase, savinase, degummase, papain, trypsin)	Effective, eco-friendly; no effluent issues	Expensive; sericin undergoes degradation; time-consuming
Heat	Boiling in water, optionally with high pressure (e.g., autoclaving)	Simple, low-cost; no purification required; eco-friendly	High temperatures degrade sericin; damages fibroin; only removes outer sericin layer

3. Applications of Sericin

Traditionally viewed as a waste product in the silk industry, sericin is now recognized for its remarkable properties, including film-forming capabilities, moisture retention, and biodegradability. These characteristics have propelled its use in industries such as cosmetics, pharmaceuticals, nutraceuticals, and biomedical applications. For instance, in cosmetics, sericin is valued for its moisturising and anti-ageing effects, while in pharmaceuticals, it serves as a biocompatible material for drug delivery systems. Despite the growing interest and utilisation of sericin, it is important to note that this review is not exhaustive; there remains a wealth of potential applications yet to be explored. Ongoing research could further elucidate the possibilities of sericin, paving the way for innovative solutions that leverage its unique properties in emerging fields such as tissue engineering, smart textiles, and environmental sustainability. (Kundu et al., 2008; Silva et al., 2022; Shitole et al., 2020; Fatahian et al. 2022).

3.1. Cosmetics

Sericin’s moisturising, anti-ageing, and UV-protection properties make it an excellent ingredient for skincare products. Its high serine content forms a protective film over the skin, enhancing moisture retention and reducing wrinkles. Studies indicate that sericin-based creams improve skin elasticity and smoothness, making them popular in anti-ageing formulations. Sericin is also used in hair care products due to its film-forming ability, which strengthens and smoothens hair (Seo et al., 2023; Rangi & Jajpura, 2015).

3.2. Pharmaceuticals & Medical Textiles

Due to its biocompatibility and biodegradability, sericin is increasingly being used in drug delivery systems and wound healing products. Sericin-based hydrogels and films are known for controlled drug release, allowing for sustained treatment while being safely biodegradable. Additionally, sericin’s antioxidant and antimicrobial properties contribute to faster wound healing and tissue regeneration, making it ideal for use in biomedical materials Sericin is also being incorporated into medical textiles due to its ability to promote skin hydration and healing. Sericin-coated textiles are used in wound care products, such as bandages and dressings, which help in the recovery process by maintaining moisture and reducing inflammation (Shitole et al., 2020; Silva et al., 2022).

3.3. Biomedicals & Tissue Engineering

Sericin shows promising potential in tissue engineering, where it serves as a scaffold for cell growth and tissue regeneration. It promotes cell adhesion and proliferation, enhancing the effectiveness of tissue-engineered scaffolds. Sericin-based hydrogels and films are currently being researched for their applications in regenerative medicine, particularly in wound healing (Hassan et al., 2024; Veiga et al., 2024).

3.4. Nutraceuticals

Sericin is rich in protein and has strong antioxidant properties, making it valuable in the nutraceutical industry. It enhances the nutritional profile of food products and acts as a natural preservative due to its ability to scavenge free radicals. This makes sericin a promising ingredient in health supplements and functional foods (Fatahian et al., 2022; Sarangi et al., 2023).

3.5. Drug Delivery

Sericin’s film-forming ability and biodegradability have made it a valuable material for controlled drug delivery systems. Sericin-based nanoparticles are being researched for their potential in cancer treatment and wound healing, as they allow for targeted and sustained release of drugs (Kundu et al., 2008, Ghaffari-Bohlouli et al., 2023).

4. Future Outlook

The future of sericin research lies in improving extraction techniques to maximise yield and purity while minimising environmental impact. Further exploration into its use in smart textiles, advanced wound healing, nutraceutical applications and regenerative medicine holds immense potential. Sustainable production methods will be crucial to scaling up the commercial viability of sericin-based products.

5. Conclusion

Sericin, once discarded as waste, has now emerged as a valuable biopolymer with applications in cosmetics, pharmaceuticals, biomedicine, and nutraceuticals. This review has highlighted its versatile uses, promising potential, and the need for continued research to unlock further opportunities in sustainable industries.

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