Jojoba's Leftover Cake, Fermented, Shows Measurable Collagen Signal in New Peer-Reviewed Study

Jojoba cake is the leftover solid mass from pressing jojoba oil out of Simmondsia chinensis seeds, and until now it has mostly gone to two places: compost piles and furnaces. A new study in the International Journal of Cosmetic Science, published EarlyView, describes what happens when that byproduct is fermented instead of discarded, and lays out in vitro and clinical evidence for what the resulting ferment can and cannot do on skin.

The research team, led by James V. Gruber alongside Amber Schwartz, Nicole Terpak, Robert Holtz and coauthors from Brazil-based labs, fermented aqueous jojoba cake with three separate microorganisms: Lactobacillus plantarum, Saccharomyces cerevisiae and Streptococcus thermophilus. According to the paper, the cake already contains the proteins, sugars and lipids needed to sustain bacterial fermentation on its own, and the process breaks down those proteins into amino acids and peptides that the raw cake does not offer. The authors are explicit that this distinction matters: the unfermented cake, in their words, 'is not suitable for topical applications,' while fermentation 'produces components more suitable for topical care.'

To find out which ferment actually did something to skin cells, the researchers ran human genomic microarrays on 3D tissue models, screening more than 244 genes with known skin functions. The Lactobacillus plantarum ferment stood out with the strongest upregulation across that panel, which is what pushed it forward for closer testing. ELISA protein assays on skin cell cultures then confirmed dose-dependent increases in three specific proteins: collagen-1A1, protocadherin-18 and opioid growth factor receptor. That progression from a broad genomic screen to three named proteins is the load-bearing evidence in the paper, and it is worth keeping separate from any claims about visible results, since ELISA assays measure protein levels in cultured cells, not wrinkles on a face.

The clinical portion narrows the claim further. Forty-six people used a cream with 1.0% of the Lactobacillus ferment for 56 days, and the researchers tracked collagen using diffuse reflectance spectroscopy, a technique that reads collagen fluorescence in skin rather than relying on self-reported texture or photographs. The paper reports a statistically significant increase in that fluorescence signal at both Day 28 and Day 56 compared to both baseline and a placebo cream, with additional fluorescence mapping done on individual subjects across the three time points. That is a measurement of one biomarker in one specific formulation at one concentration, tested against placebo, over eight weeks, on the population enrolled in this study.

What the paper documents, then, is a defined chain: an intractable oil-extraction byproduct, a specific fermentation microbe, a specific downstream ferment, three named upregulated proteins, and a clinical collagen-fluorescence readout at a stated dose and duration. What it does not document is how that ferment performs in a finished formulation at different concentrations, on other skin types, or over longer timeframes, and the study makes no claims about scalp care outcomes despite jojoba's traditional association with hair and scalp products. Any marketing built on this ingredient will need to draw that same line the authors drew: between what a 56-day, 46-person, single-concentration study measured, and everything a jojoba cake ferment might eventually be sold to do.