Impact of protectants on drying kinetics and viability of microwave freeze-driedLactobacillus paracaseissp.paracaseiF19

Abstract

The three carbohydrates sorbitol, trehalose, and maltodextrin, differing in molecular weight, were investigated as excipients to enhance survival of the probiotic strain Lactobacillus paracasei ssp. paracasei F19 during a microwave‐assisted freeze‐drying process. This technique was further compared to conventional freeze‐drying, where thermal energy is supplied by heat conduction instead of radiant energy. Survival rates revealed similar values for both techniques after drying without protectants (~10%). While addition of maltodextrin and trehalose led to a two‐ up to threefold increase in survival for both dryings, sorbitol containing samples showed the greatest difference between the two techniques: 65% after freeze‐drying versus 12% after microwave freeze‐drying. Though protection mechanisms were generally found to be equal to conventional lyophilization, microwaves are likely to induce vibrations in the hydrophilic sugars. Thus, not all protectants which are applicable in freeze‐drying, can be applied in microwave freeze‐drying to enhance bacterial viability. Practical applications A new drying process for the efficient preservation of bacterial cultures, such as lactic acid bacteria, was investigated. Microwave freeze‐drying is a much faster and less costly process than conventional freeze‐drying leading to equal product qualities and reducing the problem that drying often is the bottleneck in industrial biotechnological processes. However, no work on microwave freeze‐drying of bacterial cultures has been published so far. Knowledge on the impact of protectants on the survival of the cultures is a crucial aspect to make microwave freeze‐drying applicable in industrial processes. The selection of proper protectants is important to achieve high survival after drying and during storage.

Lyoprotectant Formulation and Optimization of the J-Aggregates Astaxanthin/BSA/Chitosan Nanosuspension

“…The above situation keeps the protein structure on the surface of nanoparticles unchanged, avoiding agglomeration of nanoparticles and maintaining nanoscale stability [ 35 ]. Sorbitol is a low molecular weight, so it may adsorb back to the nanoparticle surface and protect them [ 15 ]. In addition, sorbitol has a shallow redox potential and can replace proteins that are oxidized first, and is, therefore, considered an antioxidant [ 34 ].…”

“…Maltose and sorbitol are commonly used as lyophilization protectants [ 43 , 44 , 45 , 46 ]. Our experiments demonstrated that maltose and sorbitol can effectively protect ABC-NPs with J-type astaxanthin aggregates which have various bioactive function [ 47 , 48 ], presumably because their surfaces contain a large number of hydrogen bonds that can provide support for nanoparticles and have a high glass transition temperature [ 15 , 16 , 20 ]. Oligomannose is not commonly seen in previous studies.…”

“…According to the references [ 25 ] and the results of the preliminary experiments, the following six lyophilization protectants, which are L-lysine [ 26 ], maltose [ 27 ], oligomannose [ 28 ], chitosan [ 29 ], mannitol [ 30 ], and sorbitol [ 15 ] were selected. The final concentrations of oligomannose, chitosan, and mannitol lyophilized protectants were 0.005%, 0.025%, 0.05%, 0.25%, and 0.5% ( w / v ).…”

“…In addition, the proteins on the surface of the nanoparticles may also undergo structural changes due to mechanical forces [ 14 ]. Appropriate lyophilization protectants can provide support in ABC-NPs, such as sugars, hydroxy alcohols, amino acids, and monosaccharide mixtures [ 15 , 16 ]. Among them, sugars are classified as monosaccharides, disaccharides, and glycans.…”

The Concept of Microwave Foam Drying Under Vacuum: A Gentle Preservation Method for Sensitive Biological Material

“…Maltodextrin, for example, is one of the most widely used polysaccharides in the food industry and has been applied as thickener, stabilizer, and foam enhancer in various products (Belitz, Grosch, & Schieberle, ; Febrianto et al., ). It additionally revealed protective effects toward lactic acid bacteria during drying and storage (Ambros, Foerst, & Kulozik, ; Ambros, Hofer, & Kulozik, ; Strasser, Neureiter, Geppl, Braun, & Danner, ; Yao et al., ).…”