Biotechnological Production
Currently, lactobionic acid is produced by chemical synthesis using refined lactose
as feedstock. This process is expensive due to the energy demand. Alternatively,
Acidic Organic Compounds in Beverage, Food, and Feed Production 111
enzymatic processes have been suggested. For example, lactose could be reacted to
lactobionic acid using an enzymatic system with co-factor regeneration. First,
lactose is converted to lactobionolactone by a cellobiose dehydrogenase. This
reaction requires an electron acceptor, which is regenerated by a laccase reducing
oxygen to water. Finally, lactobionolactone spontaneously hydrolyzes to lactobionic
acid.
Moreover, microbial production of lactobionic acid has been described. In
a fed-batch cultivation of Burkolderia cepacia growing in a complex medium
(lactose, salts, peptone, and yeast extract), a final titer of 400 g.L-1, a yield of
approximately 1.0 g of lactobionic acid per gram of lactose, and a productivity of
1.67 g.L-1.h-1 have been achieved.
Another promising strategy for an inexpensive biotechnological process is the
utilization of cheap raw materials. For example, lactobionic acid could be obtained
from concentrated cheese whey by fermentation with Pseudomonas taetrolens. In
a fed-batch process, a product concentration of 164 g.L-1 with a productivity of
2.05 g.L-1.h-1 and a yield of 0.82 g of lactobionic acid per gram of lactose have
been observed. Furthermore, whole-cell biocatalysis using permeabilized
Zymonmonas mobilis cells and an equimolar mixture of lactose and fructose has
been tested. In a batch process, a maximum lactobionic acid concentration of
268 g.L-1 and a conversion rate of 72 % within 24 h have been measured. The
productivity of lactobionic acid was 11.2 g.L-1.h-1 .
Purification Methods
Crystallise lactobionic acid from water by addition of EtOH. [NMR: Taga et al. Bull Chem Soc Jpn 51 2278 1978, Beilstein 17 III/IV 3392, 17/7 V 436.]
