Design of microcapsules containing Lactococcus lactis subsp. lactis in alginate shell and xanthan gum with nutrients core

• Alginate/xanthan gum (A/X) core–shell microcapsules containing Lactococcus lactis were developed.
• The aqueous core composition of the microcapsules did not affect alginate network stability.
• Physiological state of L. lactis during encapsulation affected bacterial survival and nisin activity.
• A/X aqueous-core microcapsules with glucose-enriched M17 exhibited antilisterial activity.

Aqueous-core microcapsules with sodium alginate (SA) hydrogel in membrane and xanthan gum (XG) in core were prepared using ionotropic gelation method to encapsulate bacteriocin-producing lactic acid bacteria (LAB). In this study LAB were immobilized in microcapsule membrane. XG was applied to reinforce SA microcapsules. Molecular interaction between SA and XG in the microcapsules was investigated using FTIR spectroscopy. Microcapsules morphology and mechanical properties were examined. The impact of an enrichment with nutrients of core (M17 broth supplemented with 0.5% glucose vs physiological water) and physiological state of Lactococcus lactis during encapsulation step (exponential vs stationary state) was studied on L. lactis survival, nisin release. Furthermore, the antimicrobial effectiveness of the best system to preserve bacterial survival and permit nisin release was studied against Listeria monocytogenes.No differences were observed in terms of mechanical properties among studied systems. FTIR spectroscopy confirmed the establishment of possible hydrogen bonding between XG hydroxyls groups and SA carboxylate groups which could modify microcapsules release properties. Microcapsules with L. lactis in exponential state encapsulated in SA membrane and aqueous-core based on XG with nutrients gave the best results. At 30 °C, a complete inhibition of L. monocytogenes growth throughout the storage period was observed for these microcapsules.