Novel device to reduce milk lactose
doi:10.1038/nindia.2012.111 Published online 28 July 2012
Researchers have designed a novel device by attaching the beta-galactosidase enzyme to a graphene nanosheet. The enzyme-attached device could be used to reduce lactose, making it useful in the food industry for manufacturing low-lactose products.
In lactose-intolerant individuals, beta-galactosidase enzyme comes to the rescue by reducing lactose and producing galactooligosaccharides (GOS), a prebiotic known to aid the growth of bifidobacteria in the colon. Enzymes such as beta-galactosidase are too expensive to be discarded after a single use, which makes their commercial exploitation uneconomical.
It is possible to overcome this issue by using a suitable support material to which enzymes could be attached and reused. To find such a material, the researchers turned their attention to graphene.
First, they produced a graphene nanosheet using graphite oxide and modified it with chemical reagents. Next they extracted beta-galactosidase enzyme from chickpea seeds and attached the enzyme to the nanosheet using organic compounds such as cysteamine and glutaraldehyde.
The researchers then studied the efficacy of the enzyme-attached nanosheet for reducing lactose in milk and whey. The device successfully reduced lactose in both samples to produce GOS. When stored at 4 °C, the attached enzyme retained more than 94% residual activity after four months in both dry and wet conditions. At room temperature, after two months the enzyme demonstrated residual activities of 91% and 83% when stored in dry and wet conditions, respectively.
When stored at 4 °C, the attached enzyme showed excellent reusability, with negligible loss up to three cycles and more than 92% enzymatic activity after ten cycles of repeated use.
"In the cheese industry, lactose is a waste," says lead researcher Arvind M. Kayastha. "The conversion of lactose into a highly valuable product such as GOS using immobilized beta-galactosidase is therefore of significant interest to the food industry," he adds.
The authors of this work are from: School of Biotechnology, Faculty of Science, and Nanoscience and Nanotechnology Unit, Department of Physics, Banaras Hindu University, Varanasi, India.