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Prediction of frozen virus stability based on degradation mechanisms, real-time data and modeling. Bioanalysis 2022; 14:1177-1190. [DOI: 10.4155/bio-2022-0101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Aim: Critical virus reagents in regulated bioanalytical assays require stability monitoring. Although stability at ultralow frozen temperatures is generally assumed, published data are limited and real-time studies are time consuming. Materials & methods: The authors reviewed literature data, typical mechanisms of molecular degradation, glass transition temperatures of commonly used buffers and available real-time storage data to model frozen virus reagent stability. Results: Storage at ultralow temperatures below the glass transition temperature was critical for virus stability. Modeling of real-time data suggested that virus potency remained within 0.5 log10 of its starting potency at a probability of >99, 90 and 73% after 10, 20 and 30 years, respectively. Conclusion: The study supports the practice of virus storage at -70°C or below for 20–30 years.
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Sogabe T, Nakagawa H, Yamada T, Koseki S, Kawai K. Effect of water activity on the mechanical glass transition and dynamical transition of bacteria. Biophys J 2022; 121:3874-3882. [PMID: 36057786 PMCID: PMC9674979 DOI: 10.1016/j.bpj.2022.09.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2022] [Revised: 08/01/2022] [Accepted: 08/31/2022] [Indexed: 11/30/2022] Open
Abstract
The purpose of this study was to clarify the glass-transition behavior of bacteria (Cronobacter sakazakii) as a function of water activity (aw). From the water sorption isotherm (298 K) for C. sakazakii, monolayer water content and monolayer aw were determined to be 0.0724 g/g-dry matter and 0.252, respectively. Mechanical relaxation was investigated at 298 K. In a higher aw range of over 0.529, the degree of mechanical relaxation increased with an increase in aw. From the effect of aw on the degree of mechanical relaxation, the mechanical awc (aw at which mechanical glass transition occurs at 298 K) was determined to be 0.667. Mean-square displacement of atoms in the bacteria was investigated by incoherent elastic neutron scattering. The mean-square displacement increased gradually with an increase in temperature depending on the aw of samples. From the linear fitting, two or three dynamical transition temperatures (low, middle, and high Tds) were determined at each aw. The low-Td values (142-158 K) were almost independent from aw. There was a minor effect of aw on the middle Td (214-234 K) except for the anhydrous sample (261 K). The high Td (252-322 K) largely increased with the decrease in aw. From the aw dependence of the high Td, the dynamical awc was determined to be 0.675, which was almost equivalent to the mechanical awc. The high Td was assumed to be the glass-transition temperature (Tg), and anhydrous Tg was estimated to be 409 K. In addition, molecular relaxation time (τ) of the bacteria was calculated as a function of aw. From the result, it is suggested that the progress of metabolism in the bacterial system requires a lower τ than approximately 6 × 10-5 s.
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Affiliation(s)
- Tomochika Sogabe
- Graduate School of Integrated Sciences for Life, Hiroshima University, Higashi-Hiroshima, Hiroshima, Japan
| | - Hiroshi Nakagawa
- Materials Sciences Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki, Japan; J-PARC Center, Japan Atomic Energy Agency, Tokai, Ibaraki, Japan
| | - Takeshi Yamada
- Neutron Science and Technology Center, Comprehensive Research Organization for Science and Society (CROSS), Tokai, Ibaraki, Japan
| | - Shigenobu Koseki
- Research Faculty of Agriculture, Hokkaido University, Sapporo, Hokkaido, Japan
| | - Kiyoshi Kawai
- Graduate School of Integrated Sciences for Life, Hiroshima University, Higashi-Hiroshima, Hiroshima, Japan.
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Cao R, Sogabe T, Mikajiri S, Kawai K. Effects of sucrose, carnosine, and their mixture on the glass transition behavior and storage stability of freeze-dried lactic acid bacteria at various water activities. Cryobiology 2022; 106:131-138. [PMID: 35181277 DOI: 10.1016/j.cryobiol.2022.02.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 02/07/2022] [Accepted: 02/12/2022] [Indexed: 11/03/2022]
Abstract
Effects of sucrose, carnosine, and their mixture on the glass transition behavior and storage stability of freeze-dried Lactobacillus reuteri at various water activities (aw) were investigated. At aw = 0.328, the control (non-additive sample) showed viable cells as uncountable after storage at 25 °C for 4 weeks. The sucrose and sucrose-carnosine samples showed clear glass transition at a slightly lower temperature than the storage temperature, and maintained a large number of viable cells after storage. The carnosine sample crystalized during the storage, and a large reduction in viable cells was observed. At aw = 0.576, the samples showed a small endothermic shift due to glass transition, suggesting partial crystallization. The Tg decreased with increases in aw because of the water plasticizing effect. After storage, the sucrose-carnosine sample showed much higher viable cell numbers than the other samples. At aw = 0.753, the sucrose and sucrose-carnosine samples showed clear glass transition. The carnosine sample showed freeze-concentrated glass transition and subsequent ice melting. After storage, the sucrose and carnosine samples showed an uncountable and a low number of viable cells, respectively, but sucrose-carnosine maintained relatively high viable cell numbers. In addition, carnosine strongly supported the stabilizing effect of sucrose (even at low additive levels) depending on the aw. These results suggest that sucrose-carnosine shows a synergistic stabilizing effect.
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Affiliation(s)
- Ruodan Cao
- Program of Food and AgriLife Science, Graduate School of Integrated Sciences for Life, Hiroshima University, 1-4-4 Kagamiyama, Higashi-Hiroshima, Hiroshima, 739-8528, Japan
| | - Tomochika Sogabe
- Program of Food and AgriLife Science, Graduate School of Integrated Sciences for Life, Hiroshima University, 1-4-4 Kagamiyama, Higashi-Hiroshima, Hiroshima, 739-8528, Japan
| | - Shuto Mikajiri
- Graduate School of Biosphere Science, Hiroshima University, 1-4-4 Kagamiyama, Higashi-Hiroshima, Hiroshima, 739-8528, Japan
| | - Kiyoshi Kawai
- Program of Food and AgriLife Science, Graduate School of Integrated Sciences for Life, Hiroshima University, 1-4-4 Kagamiyama, Higashi-Hiroshima, Hiroshima, 739-8528, Japan; Graduate School of Biosphere Science, Hiroshima University, 1-4-4 Kagamiyama, Higashi-Hiroshima, Hiroshima, 739-8528, Japan.
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Le TND, Matsumoto A, Kawai K. Effects of Trehalose Content and Water Activity on the Fracture Properties of Deep-fried Wheat Flour Particles and Freeze-dried Porous Waxy Corn Starch Solids. J Appl Glycosci (1999) 2021; 68:69-76. [PMID: 34853548 PMCID: PMC8611405 DOI: 10.5458/jag.jag.jag-2021_0007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Accepted: 07/09/2021] [Indexed: 11/23/2022] Open
Abstract
Wheat flour-based batter containing 0 to 20 % trehalose was deep-fried, dried and held in various water activity (aw) conditions. The effects of trehalose content and aw on oil content, water sorption, isothermal mechanical relaxation, and fracture properties were investigated. For comparison, the fracture properties of freeze-dried porous waxy corn starch solids were also investigated. The 10 % trehalose sample had the lowest oil content, water content, and aw. A force-reduction value (∆F) of the samples was evaluated as a typical mechanical relaxation parameter. ∆F gradually increased with increasing aw and sharply increased above a specific aw presumed to be associated with the glass to rubber transition. Compared to ∆F values among the glassy samples, 10 and 20 % trehalose samples had higher ∆F values (were more rigid) than 0 and 5 % trehalose samples. From the fracture measurements of the glassy samples, the first fracture force increased linearly and the number of fracture peaks decreased linearly with increasing aw. At each aw, 10 % trehalose had the lowest first fracture force and the highest the number of fracture peaks. Freeze-dried porous waxy corn starch solids showed similar fracture properties to deep-fried samples. These findings suggest that around 10 % trehalose content is optimal for producing deep-fried foods with a brittle texture.
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Affiliation(s)
| | - Akane Matsumoto
- 1 Graduate School of Integrated Sciences for Life, Hiroshima University
| | - Kiyoshi Kawai
- 1 Graduate School of Integrated Sciences for Life, Hiroshima University
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Kawai K, Sato K, Lee K, Koseki S. Effects of glass transition and hydration on the biological stability of dry yeast. J Food Sci 2021; 86:1343-1353. [PMID: 33655495 DOI: 10.1111/1750-3841.15663] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Revised: 01/28/2021] [Accepted: 02/03/2021] [Indexed: 11/28/2022]
Abstract
The purpose of this study was to determine the effects of glass transition and hydration on the storage stability of baker's dry yeast (Saccharomyces cerevisiae). The glass transition temperature (Tg ) of the yeast decreased with increase in water activity (aw ), and aw at which glass transition occurs at 25 °C was determined as the critical aw (awc ). From mechanical relaxation measurements at 25 °C, the yeast exhibited a large mechanical relaxation above the awc , and the degree of mechanical relaxation increased gradually with increasing aw . This behavior corresponded to a gradual increase in molecular mobility with increasing aw in the rubbery liquid state. Freezable water was observed from aw ≥0.810, and the proportion of freezable water increased with increasing aw . Examination of the effect of aw on the residual biological activity of yeast samples stored at 25 °C for 30 days revealed maximum residual biological activity at aw = 0.225 to 0.432. In the lower aw range, the residual biological activity decreased because of oxidation of lipids. In the higher aw range, the residual biological activity decreased gradually with increasing aw . The yeast samples maintained a relatively high residual biological activity, because they could maintain relatively low molecular mobility even in the rubbery liquid state, as suggested by their mechanical relaxation behavior. At aw ≥0.809, residual activity decreased to a negligible value. This could be explained by the appearance of secondary hydrate water (freezable water). Hydrate water protects yeast cells from lipid oxidation but reduces the Tg . As a result, the yeast cells are stabilized maximally only at the awc . PRACTICAL APPLICATION: Although the growth rate of yeast cells becomes negligible below a certain aw , the biological activity of dry yeast decreases gradually during storage. The fact that dry yeast can be maximally stabilized at the awc is practically useful as a criterion for controlling storage stability. In addition, it was found that a remarkable reduction in the molecular mobility, which is otherwise ordinarily increased due to the glass-to-rubber transition, is prevented in yeast. It is possible that the crystallization of amorphous sugar can be prevented by yeast extract. The suggested effect is expected to result in enhanced quality of carbohydrate-based foods.
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Affiliation(s)
- Kiyoshi Kawai
- Graduate School of Integrated Sciences for Life, Hiroshima University, 1-4-4 Kagamiyama, Higashi-Hiroshima, Hiroshima, 739-8528, Japan.,Graduate School of Biosphere Science, Hiroshima University, 1-4-4 Kagamiyama, Higashi-Hiroshima, Hiroshima, 739-8528, Japan
| | - Kyoya Sato
- Graduate School of Biosphere Science, Hiroshima University, 1-4-4 Kagamiyama, Higashi-Hiroshima, Hiroshima, 739-8528, Japan
| | - Kyeongmin Lee
- Graduate School of Agricultural Science, Hokkaido University, Kita 9 Nishi 9, Sapporo, Hokkaido, 060-8589, Japan
| | - Shigenobu Koseki
- Graduate School of Agricultural Science, Hokkaido University, Kita 9 Nishi 9, Sapporo, Hokkaido, 060-8589, Japan
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