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27/03/26PCEDS3889v5EN Page 1 of 18 KeraBio™ K31 Biomimetic bond-builder with pure, potent performance. Keratin-recharge at the molecular level, elevating hair strength beyond repair. Designed to work in harmony with the hair, it empowers reinvention, helping consumers reconnect with hair that feels resilient, expressive and truly their own. INCI name Preservative system % Active Recommended use level Appearance Average molecular weight (Da) Aqua and Hydrolyzed sr- (Tripeptide-137 Hexapeptide- 40 sh-Polypeptide-184 sh- Polypeptide-146) Benzyl alcohol 5% Up to 2% as supplied (0.1% active) Yellow amber liquid ~900 Features • Biotechnology production process • 99% naturally derived (ISO 16128) • Vegan* suitable • Readily biodegradable (OECD 301F) • Non-aquatoxic • Phenoxyethanol-free • EU and UK REACh compliant Benefits • Forms durable bonds with peptides (peptide binding assay) • Delivers a keratin recharge through biomimetic integration (fluorescence microscopy) • Builds 100% stronger hair than the leading commercial bond builder (cyclic fatigue at 0.1% active) • The more often you use it, the stronger your hair gets (cyclic fatigue and DSC, multi-application data) • Reinforces resilience before transformation (cyclic fatigue and DSC, pre-chemical service, at 0.5% active) • 360° root-to-tip repair, enhancing manageability and pre-styling performance (consumer study) Formats • Suitable for all formats (versatile chemistry means it can be formulated into a wide range of formulation types). Hair types • Damaged to overprocessed hair (bleached, coloured hair, heat damaged). • Fragile hair types SKUs • Damaged hair, coloured hair, ageing hair *can be considered to be generally suitable for vegan; however, as there is no single agreed definition nor a standard, global certification, if you are interested in making a vegan claim, please request our Vegan Suitability statement for specifics on this product, and compare to the certification(s) you are seeking to meet. 27/03/26PCEDS3889v5EN Page 2 of 18 The bond builder market: a high-growth opportunity The bond builder category is expanding rapidly as consumers seek stronger, healthier hair amid frequent colour transformations, chemical treatments, and heat styling. While many products claim to strengthen and protect, true bond builders remain rare. Now, Croda Beauty is redefining the landscape by introducing the first bond-building solution developed by a supplier using biotechnology, offering brands a cutting- edge, science-backed approach to hair repair. Biotechnology designed and produced Over a decade of advanced proteomics research has deepened our understanding of hair at the molecular level, allowing us to push the boundaries of hair repair science. Using synthetic biology, we have engineered a keratin protein previously unattainable with conventional technology. Unlike traditional proteins derived from animal or plant sources, KeraBio K31 is biomimetic, designed to work in harmony with the hair’s natural biology. Its human hair-identical structure preserves key active sites within the peptide sequence, ensuring elevated potency and unrivalled repair performance. Biotechnology production process Overview Inspired by nature, our biotechnology process leverages advanced digital tools to design proteins with targeted functions. Guided by biological insights and powerful bioinformatics, we engineer microbial cell factories to produce these proteins efficiently. Each strain undergoes rigorous testing to ensure performance in real-world applications. The most effective strain is then optimised through lab-scale fermentation, where we fine-tune growth conditions to maximise protein yield. Following production, we apply advanced purification and solubilisation techniques to achieve exceptional quality and performance. This streamlined process, from design to industrial-scale fermentation, transforms breakthrough science into high-impact, commercially viable solutions. The DBTL (Design-Build-Test-Learn) cycle In developing KeraBio K31, an iterative engineering biology cycle was followed, first starting with an in-silico study to design multiple hair keratins, carefully selecting the best candidates for production. Using genetically modified microorganisms, strains capable of producing these keratins were then constructed and samples prepared for efficacy screening in the desired applications. Each cycle provided valuable insights, allowing for optimisation of the testing protocols. The two main selection criteria were performance on hair and production efficiency, both critical for transforming a lab discovery into a viable market-ready product. Scaling up for fermentation Identification of the best-performing keratin for KeraBio K31 enabled progression to scale-up studies where fermentation parameters were optimised to maximise keratin yield. The process involved cultivating genetically modified microorganisms under carefully controlled conditions, using sugar as an energy source and nitrogen as a key component for cell growth and keratin production. Creating the ideal environment for these microorganisms was essential to ensuring the efficient production of high-quality keratin at scale. Purification and final processing To meet the high-quality and performance standards of KeraBio K31, advanced purification and solubilisation techniques were developed. Following fermentation, downstream processing was carried out, starting with harvesting the keratin-producing cells. A series of purification steps then isolated the keratin at increasing levels of purity. Finally, enzymatic hydrolysis converted the purified keratin into the desired peptide sizes, ensuring KeraBio K31 was optimised for best performance across various applications. 27/03/26PCEDS3889v5EN Page 3 of 18 Summary Through a precision-engineered process, spanning in-silico design, lab-scale optimisation, and large-scale fermentation, KeraBio K31 was brought to life at an industrial scale. This innovative approach transforms breakthrough science into a commercially viable ingredient, elevating hair repair beyond conventional bond-building. KeraBio K31 is preserved with benzyl alcohol and supplied as a 5% active solution in water, ensuring stability and seamless incorporation into a wide range of cosmetic formulations. Performance studies The performance benefits of KeraBio K31 have been evaluated using a series of laboratory tests: Hair fibre penetration Keratin binding studies Cyclic Fatigue testing Differential Scanning Calorimetry (DSC) testing Consumer use study Hair penetration and hair bonding Fluorescence microscopy To assess the penetration of KeraBio K31 into hair fibres, a fluorescence labelling and microscopy approach was employed. KeraBio K31 was conjugated with 5(6)-carboxytetramethylrhodamine N-succinimidyl ester (TAMRA SE), producing a fluorescent protein with excitation and emission maxima at approximately 540 nm and 588 nm, respectively, avoiding interference from hair autofluorescence. Unbound dye was removed through washing and filtration to ensure signal specificity. The labelled protein solution (0.2–0.7%) was applied topically to hair fibres across three treatment regimens: 1, 5 and 10 applications. After each treatment, fibres were rinsed to remove non-bound material. Treated fibres were embedded, cryosectioned into 10 µm slices, and mounted onto glass slides for imaging. Fluorescence microscopy was performed using a Leica DM2500 system with a CY3/TRITC filter set. Images were captured under consistent conditions using a 20x objective. This approach enabled clear visualisation of KeraBio K31 within the hair fibre, confirming its ability to penetrate and localise within internal structures. Results are shown in Figure 1. Additionally, fluorescence images of hair cross-sections were segmented into red, blue, and yellow channels, converted to grayscale, and averaged to determine the concentration of fluorescence-labelled KeraBio K31. Variations in concentration were analysed by measuring grayscale intensity from the hair surface to the centre. This was achieved by averaging grey values along multiple lines spanning from the surface to the centre across 10 hair cross-sections. The resulting intensity profiles are presented in Figure 2 and a graph comparing penetration after 1, 5 and 10 applications is shown in Figure 3. This microscopic analysis of hair fibres treated with fluorescently labelled KeraBio K31 demonstrates a dose-dependent increase in peptide penetration into the hair cortex with each successive application. Specifically, fluorescence imaging reveals a progressive accumulation of the labelled peptide within the cortical region of the hair fibre, correlating with the number of applications. These findings highlight KeraBio K31’s ability to recharge keratin within the hair, restoring the hair’s structural integrity. 27/03/26PCEDS3889v5EN Page 4 of 18 Figure 1: Fluorescence microscopy images of KeraBio K31 penetrating hair Figure 2: Graph of fluorescence intensity versus distance from hair surface for KeraBio K31 Figure 3: Fluorescence intensity of KeraBio K31 after 1, 5 and 10 applications, showing the cortex penetration increases with repeated application 27/03/26PCEDS3889v5EN Page 5 of 18 Peptide binding study The structural integrity of hair is defined by its keratin composition, where specific amino acid sequences drive the formation of distinct architectures within the fibre. To better understand how KeraBio K31 interacts with these structures, a targeted peptide binding assay was developed. This assay evaluated the binding of KeraBio K31 to protein sequences found within human hair. Full keratin amino acid sequences were systematically subdivided into smaller peptide fragments, representing a range of keratin types, including acidic, basic, and keratin-associated protein (KAP) sequences. Each peptide fragment was then immobilised onto the base of ind...