Two Prebiotics for the Price of One: Inside DMK's Patent for High-Lactulose GOS

DAIRY & ALTERNATIVES NUTRACEUTICALSINFANT NUTRITION

Harleen Singh

7/17/20265 min read

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Germany's largest dairy cooperative is betting that a prebiotic ingredient with built-in lactulose could carve out a distinct position in an increasingly crowded gut-health market.

DMK filed an European patent application EP4762936A1 in December 2024. Published on 24 June 2026, it covers a galactooligosaccharide (GOS) composition enriched with unusually high levels of lactulose, along with the enzymatic process used to make it. The core claim is straightforward: a GOS product that simultaneously delivers two well-established prebiotic compounds in a single ingredient, produced cleanly enough to qualify for food and supplement use.

Why GOS Needs a Differentiator

The GOS market is mature. Commercial GOS has been produced enzymatically from lactose for decades and is used widely in infant formula, adult nutritional supplements, and functional dairy products. Major suppliers — FrieslandCampina, Clasado, Kerry, and others — have been competing on yield, purity, and specific oligosaccharide profiles. The IP landscape is correspondingly dense, with patents from Novozymes, DuPont (IFF), Valio, and multiple universities covering different enzyme sources, substrates, and production variants.

For a dairy processor entering this space, standing still on commodity GOS is not a viable strategy. DMK's angle here is compositional differentiation: their invention specifically targets a GOS mixture with a lactulose content of 5 to 20 percent by weight, with the preferred range cited as 10 to 15 percent. To put that in context, conventional GOS production — starting from straight lactose — generates very little lactulose, if any. It is largely a byproduct of the enzymatic chemistry, not a designed-in feature.

The patent's stated rationale is that both GOS and lactulose are independently recognized as prebiotics with complementary mechanisms, particularly their ability to selectively stimulate Bifidobacterium growth. Combining them into one ingredient, the applicants argue, creates a more potent prebiotic profile than either compound alone.

The Technical Mechanism: Fructose as the Key Input

The central innovation is not a new enzyme — it is the substrate. Conventional GOS production uses lactose (glucose + galactose) as the sole input. DMK's process begins with a lactose-fructose mixture, and that single change in feedstock is what drives lactulose formation.

Here is why it matters biochemically. When β-galactosidase acts on lactose, its transgalactosylation activity can transfer the galactose unit not back onto glucose (as in standard GOS synthesis) but onto a fructose molecule instead. The resulting disaccharide is lactulose — galactose-fructose — which is chemically identical to the lactulose already used as a pharmaceutical laxative and well-characterized as a Bifidobacterium growth factor.

The patent describes two enzyme routes. The so-called "neutral process" uses β-galactosidase from Bacillus circulans at pH 5.5–6.5 and 45–55°C. The "acid process" uses an enzyme from Aspergillus oryzae at pH 4–5 and 50–60°C. Both are established commercial enzymes already deployed in GOS production; the novelty lies in their application to a mixed lactose-fructose substrate rather than to lactose alone. The option to use both sequentially or in combination is also claimed.

The fructose-to-lactose ratio matters significantly. The patent specifies a fructose content of around 10 to 25 percent and a lactose content of around 20 to 50 percent in the starting solution, with preferred dry solids of 25 to 35 percent. The precise ratio will influence how much lactulose is formed versus how much of the enzyme's activity goes into standard GOS chains or hydrolysis products. The patent does not disclose an explicit optimization table relating fructose:lactose ratios to lactulose yields — a gap that patent examiners and competing formulators will both notice.

A Clever Approach to Enzyme Management

What makes the process description commercially interesting is its enzyme recycling strategy. A common cost driver in enzymatic GOS production is the enzyme itself. Conventional approaches either immobilize the enzyme on a solid support (which introduces its own process complications) or sacrifice the enzyme after each batch.

DMK's approach takes a different path. Once the GOS-plus-lactulose synthesis reaches its maximum yield — around 90 minutes in Example 1 — the enzyme needs to be stopped quickly to prevent the back-reaction, where the enzyme begins re-hydrolyzing the oligosaccharides it has just built. Rather than heat-killing the enzyme (which destroys it permanently), the patent proposes a pH shift. Raising the pH to around 9–10 via sodium hydroxide addition suppresses enzymatic activity by 80 to 90 percent without irreversibly denaturing the enzyme protein.

The partially inhibited enzyme mass is then separated by ultrafiltration through a 10 kDa membrane. The retentate — containing the enzyme — is recycled back into the reactor. Only around 5 percent fresh enzyme needs to be added per cycle to compensate for activity losses, according to Example 1. The downstream permeate carries the GOS and lactulose forward through further processing.

This is a genuinely practical engineering detail. Enzyme recycling via pH-controlled inhibition and ultrafiltration is not entirely novel in enzyme bioprocessing, but its specific application here to a mixed GOS-lactulose synthesis adds process efficiency without requiring immobilization infrastructure.

Downstream Purification: Getting Rid of Unwanted Sugars

Any enzymatic GOS synthesis generates a complex mixture. The intended oligosaccharide products are accompanied by residual lactose, monosaccharides (glucose, galactose, fructose), and short-chain sugar fragments that carry no prebiotic benefit. Removing these is essential for a clean, high-potency ingredient.

The patent describes an optional second enzymatic step where the permeat from the first ultrafiltration is treated with lactase (lactose hydrolase) and/or the yeast Kluyveromyces lactis to consume remaining lactose, breaking it down to monosaccharides or metabolizing it to CO₂ and ethanol. A second ultrafiltration then separates these enzyme/yeast masses.

The final purification step is nanofiltration through a 0.1–2 kDa membrane, which retains the larger GOS and lactulose molecules while allowing monosaccharides and small sugars to pass through in the permeate. The retained concentrate is then dried — preferably by spray drying at 180–260°C inlet and 80–105°C outlet — to a powder with no more than 5 percent residual moisture.

The single demonstrated example reports a white powder with over 75 percent GOS, 14 percent lactulose, 0.4 percent monosaccharides, and 1 percent residual moisture. These are applicant-generated data, produced at undisclosed scale, and have not been independently verified. Whether these yields are reproducible at industrial scale under varying raw material inputs remains to be demonstrated.

Commercial Context and Strategic Fit

For DMK, this patent sits at an interesting intersection of dairy processing economics and functional ingredients strategy. As Europe's largest dairy cooperative, DMK has vast access to lactose and lactose-rich streams like whey permeate — the very feedstocks this process can use. The patent explicitly allows fructose-enriched whey permeate or milk permeate as starting materials, which would let DMK valorize what are currently commodity or waste streams into a higher-margin prebiotic product.

The fructose input needed to generate lactulose during transgalactosylation could itself be sourced from an enzymatic lactose hydrolysis-isomerization sequence. The patent references a published process by Luzzi, Steffens et al. (2020) in International Journal of Dairy Technology for this purpose — notably, co-inventor Marco Steffens appears as an author on that paper, suggesting this glucose-isomerization approach is already embedded in DMK's technical toolkit.

The target applications cited in the patent are food supplements and animal feed — a broad scope that gives DMK optionality across human nutrition and the growing premium petfood and livestock prebiotic markets. Lactulose is already approved and commercially established in both human laxative products and calf milk replacers, so a GOS composition with built-in lactulose could offer a regulatory-friendly dual-prebiotic positioning without requiring novel ingredient approval in most jurisdictions.

Bottom Line

DMK's patent filing is a technically coherent attempt to create a differentiated prebiotic ingredient by exploiting the transgalactosylation activity of well-known β-galactosidases on a non-standard fructose-containing substrate. The pH-controlled enzyme recycling mechanism is a practical process engineering contribution. The resulting GOS-lactulose composition — if the 14 percent lactulose yield from the single example holds at scale — would represent a meaningfully distinct product from conventional GOS.

For ingredient buyers and R&D teams watching the prebiotic space, the more interesting question may be less about the patent itself and more about what it signals: a major European dairy processor moving up the value chain, converting commodity lactose streams into functional ingredients with dual prebiotic claims. Whether the IP holds or not, the strategic intent is clear.