L-Tryptophan
L-Tryptophan is an essential aromatic amino acid that serves as the precursor to the neurotransmitter serotonin, the pineal hormone melatonin, and the pyridine nucleotide cofactors NAD and NADP through the kynurenine pathway.
The molecule carries an indole side chain that absorbs in the ultraviolet near 280 nm, the basis for routine spectrophotometric protein quantification. It is a white to slightly yellowish crystalline powder for feed, food, and pharmaceutical use.
We source bulk L-Tryptophan from top China manufacturers for our partners, working with several of them. The manufacturers are in Jiangsu, Hebei and Heilongjiang. For this ingredient the minimum order is 500 kg, and a smaller requirement can ship in a combined container with other ingredients.
Please send the grade you need, the volume and your destination port, and we will come back with a solution and a price.
or call +86-21-6858 0751
- Minimum order
- 500 kg
- Packaging
- 25 kg kraft paper bag with PE inner liner
- ISO 9001
- HACCP
- Halal
- Kosher
Specifications
Grades / Types Available: Food Grade, Feed Grade
| Item | Specification |
|---|---|
| Appearance | White to yellowish-white crystalline powder |
| Assay | ≥98.5% |
| Specific Rotation [α]D20 | -30.0° to -33.0° |
| Loss on Drying | ≤0.5% |
| Residue on Ignition | ≤0.1% |
| pH (1% solution) | 5.5–7.0 |
| Heavy Metals (as Pb) | ≤10 ppm |
| Arsenic | ≤1 ppm |
| Ammonium | ≤0.02% |
| Total Plate Count | ≤1000 CFU/g |
| Purity (Food Grade) | 98% min |
| Moisture/Loss on Drying | < 0.5% |
| Ash | < 0.1% |
| Lead | < 1 ppm |
| Yeast & Mold | < 100 cfu/g |
Common Markets Grades
Feed, food and pharmaceutical grades of L-Tryptophan reach the market.
Feed grade at 98.5 percent minimum assay serves as the fourth limiting amino acid in many swine and poultry diets, particularly in low-protein formulations and weanling pig starter feeds.
Food and supplement grade at 98.5 to 99 percent meets FCC specifications and is used in medical foods, infant formula fortification, sports and sleep supplements, and parenteral nutrition.
Pharmaceutical grade meets USP and Ph. Eur. monographs at 98.5 to 101.0 percent on the dried basis. Amino acid infusion manufacturers buy it, as do producers of oral preparations for sleep, mood, and metabolic indications.
Applications
- Swine weanling and starter feeds as the fourth limiting amino acid
- Poultry diets in low-protein formulations
- Aquaculture feeds for salmonids and shrimp
- Pet food for dogs and cats positioned for calming and behavioral support
- Infant formula and follow-on formula fortification
- Parenteral and enteral nutrition amino acid solutions
- Sleep, mood, and stress-management dietary supplements
- Medical foods for depression, sleep disorders, and metabolic indications
- Sports nutrition and recovery products
- Cell culture media and biopharmaceutical fermentation feeds
Brands Using L-Tryptophan
Widely-distributed consumer products that list L-Tryptophan on the ingredient label.
- NOW FoodsL-Tryptophan 500 mg Veg Capsules ↗Each capsule supplies 500 mg L-tryptophan, an essential amino acid and precursor to serotonin and melatonin.Label verified 2026-05-24
- Source NaturalsSerene Science L-Tryptophan 500 mg ↗An L-tryptophan tablet supplying 500 mg per serving in the Serene Science line.Label verified 2026-05-24
- LidtkeL-Tryptophan Complete ↗Formulated with TryptoGOLD L-tryptophan plus B vitamins, curcumin, magnesium, vitamin C and L-lysine.Label verified 2026-05-24
- Source NaturalsL-Tryptophan with Coenzyme B-6 ↗Combines L-tryptophan with the coenzyme form of vitamin B-6 (P-5-P) required to convert tryptophan to serotonin.Label verified 2026-05-24
Brand names, product names and logos are the property of their owners. They appear here as published evidence that the ingredient is used, taken from the brand's own label or website. Their appearance is not an endorsement, and it does not mean the brand buys from us or from any manufacturer listed on this site.
China Manufacturers of L-Tryptophan
Top L-Tryptophan manufacturers in China.
- Hebei Huayang Biological Technology Co., Ltd.13 ingredients in the directory
Heilongjiang Jinxiang Biochemical Co., Ltd.9 ingredients in the directory
Jiangsu Quanjia Shun Health Technology Co., Ltd.12 ingredients in the directory
Wuxi Jinghai Amino Acid Co., Ltd.18 ingredients in the directory
Company names and logos are the property of the manufacturers themselves. They are listed here because our own directory records them as producing this ingredient. A listing is not an endorsement by them, and we do not represent them or speak on their behalf.
How We Help Source L-Tryptophan
Direct Factory Sourcing
We run the whole process: selecting the manufacturer from the top Chinese food ingredient producers, negotiating the price, verifying quality, and coordinating the logistics. You deal with us instead of with several factories at once.
Original Packaging and Documents from the Manufacturer
The manufacturer sends your L-Tryptophan out of its own factory in the original packing, through to your destination port. The COA, COO, MSDS, TDS and any certifications reach you from the manufacturer as well.
Free Samples and Lead Time
We send 100 to 500 g free for your own laboratory to test and you cover only the courier, usually within 2 to 3 working days. ETD is usually within 7 to 15 days once the order is confirmed, and we check that date against the factory's own manufacturing schedule before we give it to you.
Combined Shipment
We can load L-Tryptophan together with other ingredients such as Glycine, L-Arginine and L-Leucine into one 20' FCL. If your quantity is small, we can also ship LCL.
Regulatory Status
L-Tryptophan is authorised as a feed additive, food-grade amino acid, and pharmaceutical excipient in all major markets.
In the European Union it is listed in the Register of Feed Additives under functional group 3c for use in all animal species. The U.S. Food and Drug Administration recognises L-tryptophan as GRAS under 21 CFR 172.320 for use as a nutrient added to foods, and as an investigational and approved active in various pharmaceutical applications.
The regulatory history is shaped by the 1989 eosinophilia-myalgia syndrome (EMS) outbreak in the United States, which was traced to contaminants in a single batch of fermentation-derived L-tryptophan from Showa Denko. FDA imposed an import alert and effectively withdrew dietary supplement use of L-tryptophan for over a decade. The agency lifted restrictions in 2005, subject to supplier qualification and impurity-profile controls that remain in place today.
USP, Ph. Eur., and JP monographs govern pharmaceutical use. Halal and Kosher certifications are routinely available from fermentation producers.
Manufacturing Process
L-Tryptophan is produced commercially by microbial fermentation.
Engineered Escherichia coli and Corynebacterium glutamicum strains convert glucose to L-tryptophan through the shikimate and tryptophan biosynthetic pathways. Key engineering targets include deregulation of DAHP synthase, anthranilate synthase, and the tryptophan repressor TrpR, alongside deletion of tryptophanase and overexpression of dedicated tryptophan exporters.
Major producers include Ajinomoto, CJ CheilJedang, Meihua, Fufeng, and several other Chinese fermentation houses. The product is recovered by cell separation, ion exchange, activated carbon decolorisation, crystallisation, centrifugation, and vacuum drying.
Quality control includes strict monitoring for the trace contaminants that were associated with the 1989 eosinophilia-myalgia syndrome outbreak, with modern HPLC profiles routinely run against multiple reference impurity standards before release.
