Influence of different external liquids on the process outcomes of lactic fermentation in suspended capsules

Encapsulation is an innovative promising technique in the field of biotechnology, both for confining live microorganisms to promote their viability during processing and for the target delivery in the gastrointestinal tract, and for trapping active metabolites produced during a fermentation process within a carrier material, allowing their gradual release. During this work, a probiotic strain, Lacticaseibacillus paracasei CBA L74, was encapsulated using a hydrolyzed oatmeal suspension as a prebiotic carrier, by extrusion technique with CaCl2 a (1M) and alginate (1% w/v). The mini-bioreactors obtained were suspended in three different external liquids, (the same hydrolyzed oatmeal suspension used for the capsule production; a hydrolyzed oatmeal suspension with a modified pH equal to 3.3, and a hydrolyzed oatmeal suspension formulated by adding a specific concentration of dead bacteria) to evaluate whether the external liquid can help the confinement of the bacteria in the capsules. For this purpose, the fermentation process was carried out at 37°C for 24h; both capsules and external liquids were characterized by microbiological and chemical analyses. The maximum bacterial growth ( 109 CFU/mL) was reached in all the capsules, except for those suspended in the formulation with a modified pH where a bacterial charge of 3.5 x 108 CFU/mL was obtained; in any case, the bacterial confinement was not obtained. The highest lactic acid concentration (15.9 g/L) was observed for the capsules suspended in the same oatmeal suspension used for encapsulation, while the lowest one was obtained in the external oatmeal liquid with a modified pH.