Use
Laccases are multicopper-oxidases (benzenediol:oxygen oxidoreductase, EC
1.10.3.2) that are able to oxidize phenolic substrates (e.g. 2,6-dimethoxy-phenol),
aromatic amines (e.g. 1-hydroxybenzotriazole), or polycyclic aromatic hydrocarbons
(e.g. anthracene) . The oxidation of the substrate occurs via a oneelectron
reduction and is accompanied by a reduction of molecular oxygen to
water.
Most laccases are of fungal origin, but they also occur in bacteria, insects,
and plants. Due to the broad substrate range of laccases, their possible
industrial usage is widespread. Nevertheless, only few applications have been
commercialized up to now, mostly in the textile industry. In the food and feed
sector, laccases have been evaluated for different applications, such as the stabilization
of beverages, the reduction of off-flavors, the improvement of wheat
dough, and the usage of laccases as biosensors in the food processing industry.
Off-flavors in wine may occur due to microbial conversion of phenolic compounds
present in the wine itself or in the cork stoppers. In a commercial product
from Novozymes called Suberase, laccase is used for polymerization of phenolic
compounds in the cork, which act as precursors for malodors, such as pentachlorophenol
or 2,4,6-trichloroanisol.
In apple juice, addition of laccase reduced the amount of the phenolic offflavors
2,6-dibromophenol, guaiacol, and a-terpineol. Several studies used
laccases to increase the stability of apple juices by polymerization of phenols and
their subsequent removal by ultrafiltration methods. A positive side effect is
the decrease of molecular oxygen in the juice due to its consumption by laccases.
Nevertheless, desired phenols might also be oxidized; thus, the sensory attributes
and nutritional value might be altered.
The polymerization reactions catalyzed by laccases can also be used to improve
the shade of food, such as the coloration of tea-based products. In the bakery industry, laccase might be used together with proteases or xylanases to improve
the dough quality. It was proposed that laccases oxidize ferulic acid attached to the
arabinoxylan present in cereal flour. The obtained phenolic radicals can undergo a
nonenzymatic reaction, resulting in cross-linked feruloylated arabinoxylans.
In oat flour-based bread, the usage of laccase increased the loaf-specific volume
and decreased the crumb hardness. Contradictory, in another study, laccase
alone decreased the specific volume and increased the crumb hardness. A
combined usage of laccase with xylanase improved again the oat flour bread
properties.