Fibre enzymes: cellulase, xylanase, pectinase and more

Vegetables, fruit, whole grains, bran, beans and lentils all bring fibre to the table. Fibre is a type of carbohydrate, but unlike starch and sugars, most of it is not broken down by the body's own enzymes.

This article explains why, what plant fibre is made of, and what the five fibre enzymes in Goodness Digestive Enzymes work on: cellulase, hemicellulase, xylanase, pectinase and beta-glucanase.

What is fibre?

The US National Library of Medicine (MedlinePlus) describes fibre as a substance found in plants, in the fruit, vegetables and grains we eat, and as a type of carbohydrate. There are two kinds:

• Soluble fibre, found in oat bran, barley, nuts, seeds, beans, lentils, peas and some fruit and vegetables.
• Insoluble fibre, found in wheat bran, vegetables and whole grains.

The UK's National Health Service (NHS) says adults should aim for 30g of fibre a day, while most adults eat an average of about 20g. Good sources include wholegrain bread and pasta, bulgur wheat, brown rice, oats, potatoes with their skins on, pulses such as beans, lentils and chickpeas, vegetables, fruit, nuts and seeds.

Why does the body break down so little fibre itself?

Fibre is largely defined by what the body cannot do with it. MedlinePlus, in its page on carbohydrates, describes fibre as the part of food that the body does not break down, and a 2012 review in the Journal of Food Science and Technology defines dietary fibre as the part of plant material in the diet that resists enzymatic digestion.

A 2017 review in the journal Gut Microbes explains why: human enzymes are not able to digest most fibres. Fewer than 20 enzymes of this type, involved in digesting the large carbohydrates of the diet, have been identified in the human genome.

The bacteria in the gut are a different story. The same review notes that gut bacteria carry about 150 times more genes than the human genome, including an extensive set of enzymes that can break down a wide variety of fibres.

How much they break down depends on the fibre. The 2012 review groups pectin, gums and mucilages as soluble fibres that bacteria ferment well, and cellulose, hemicellulose and lignin as insoluble fibres that are less fermented. The 2017 review adds that cellulose is generally poorly fermented by gut bacteria.

What is plant fibre made of?

The 2012 review describes dietary fibre as the remains of plant cells that resist digestion, and lists its main components: cellulose, hemicellulose, pectic substances, gums, mucilages and lignin. Several of these are built into the plant cell wall, the layer around each plant cell. Each is a different kind of molecule, and each is a target for a different enzyme, which is why the plant-fibre group in Goodness Digestive Enzymes has five members.

What does cellulase work on?

Cellulase works on cellulose, which the 2012 review describes as the major component of plant cell walls: a long, unbranched chain of several thousand glucose units, not digested to any extent by the enzymes of the human digestive system.

Breaking cellulose down into glucose requires cellulase enzymes, according to a 2025 review on cellulase in the journal Foods. As the main part of the cell wall, cellulose is found in vegetables, fruit and grains.

What does hemicellulase work on?

Hemicellulase is a name for enzymes that work on hemicellulose. The 2012 review describes hemicelluloses as smaller, branched cell-wall chains built mostly from a sugar called xylose, along with galactose, mannose and arabinose.

According to a 2024 review on xylanase in the journal BioTechnologia, hemicellulose sits between the cellulose fibres of the cell wall. It is a mixed group, so breaking it down fully takes a range of enzymes working together.

What does xylanase work on?

Xylanase works on xylan, which the 2024 review describes as the dominant hemicellulose in plant cell walls. Xylanase breaks the links in the backbone of xylan.

The review gives food examples: arabinoxylans, a type of xylan, are found in wheat and rye, where they influence the quality of bread, and in the bran of corn. Because xylan is a hemicellulose, xylanase and hemicellulase both work on this part of the cell wall.

What does pectinase work on?

Pectinase works on pectin. The 2012 review describes pectic substances as part of the plant cell wall and as the "cement" that holds plant cells together. The 2017 review in Gut Microbes names apples as a source of pectin.

The food industry relies on this. A 2025 review of food enzymes in Food Science & Nutrition describes pectinase breaking down pectin, a carbohydrate found in plants, in the processing of fruit juice.

What does beta-glucanase work on?

Beta-glucanase works on beta-glucan. A 2024 review in the journal Nutrients names oats and barley as the main sources of beta-glucan, followed by wheat, rye and corn. Depending on the variety, oats contain about 6–8% beta-glucan and barley about 4–10%, mostly in the outer layers of the grain.

The same review describes beta-glucanase as the enzyme that breaks beta-glucan down, a job it does in the grain itself when it sprouts.

Which foods do the five enzymes work on?

In Goodness Digestive Enzymes, cellulase, hemicellulase, xylanase, pectinase and beta-glucanase help break down fibre in vegetables, fruit and grains.

Does this mean you need less fibre?

No. Fibre is valuable in itself, and a supplement does not replace eating plenty of it. The NHS recommends getting fibre from a variety of foods. Goodness Digestive Enzymes is a food supplement that supports healthy digestion; it does not replace a varied, balanced diet.

The fibre group is one of four. The others cover protein, starch and sugars and fats. For an overview, read What do digestive enzymes do?; fibre also comes up in Digestive enzymes, probiotics and prebiotics. The Ingredients page lists all 13 enzymes, and the How to use page gives the directions and safety notes.