Adsorption of ochratoxin A from grape juice by yeast cells immobilised in calcium alginate beads

Grape juice can be easily contaminated with ochratoxin A (OTA), one of the known mycotoxins with the greatest
public health significance. Among the different approaches to decontaminate juice from this mycotoxin, microbiological
methods proved efficient, inexpensive and safe, particularly the use of yeast or yeast products. To ascertain whether immobilisation of the yeast biomass would lead to successful decontamination, alginate beads
encapsulating Candida intermedia yeast cells were used in our experiments to evaluate their OTA-biosorption efficacy.
Magnetic calcium alginate beads were also prepared by adding magnetite in the formulation to allow fast
removal fromthe aqueous solutionwith a magnet. Calciumalginate beadswere added to commercial grape juice
spiked with 20 μg/kg OTA and after 48 h of incubation a significant reduction (N80%), of the totalOTA contentwas
achieved, while in the subsequent phases (72–120 h) OTA was slowly released into the grape juice by alginate
beads. Biosorption properties of alginate-yeast beads were tested in a prototype bioreactor consisting in a glass
chromatography column packed with beads, where juice amended with OTA was slowly flowed downstream.
The adoption of an interconnected scaled-up bioreactor as an efficient and safe tool to remove traces of OTA
from liquid matrices is discussed.