Abstract
Cryogenic machining is one of the most commonly used techniques for processing and preserving in food industry, and traditional antifreeze agents cannot regulate the mechanical stress damage caused by ice crystals formed during recrystallization or thawing. In this study, we successfully developed an express system of a novel recombinant snow flea antifreeze peptide (rsfAFP), which has significant ice recrystallization inhibition ability, thermal hysteresis activity and alters ice nucleation, thus regulating extracellular ice crystal morphology and recrystallization. We showed that rsfAFP improved the survival rate, acid-producing ability, freezing stability, and cellular metabolism activity of Streptococcus thermophilus. We further showed that rsfAFP interacts with the membrane and ice crystals to cover the outer layer of cells, forming a dense protective layer that maintains the physiological functions of S. thermophilus under freezing stress. These findings provide the scientific basis for using rsfAFP as an effective antifreeze agent for lactic acid bacteria cryopreservation or other frozen food.
Highlights
Due to the high-water activity in fresh foods, chemical reactions and microbial growth are prone to occur, leading to food deterioration[1]
Numerous studies have shown that Antifreeze proteins (AFPs) are adsorbed at the growth interface of ice crystals to increase the growth curvature of ice and increase the vapor pressure of the ice-water interface layer, thereby lowering its freezing point[27,32,38]
The regulation effect of insect AFPs on ice crystals conforms to the “Janus” effect, which includes non-icebinding faces (NIBF) and ice-binding faces (IBF)[39]
Summary
Due to the high-water activity in fresh foods, chemical reactions and microbial growth are prone to occur, leading to food deterioration[1]. An antifreeze agent is inevitably for frozen food to reduce mechanical damage caused by ice crystals during cryogenic machining or cryopreservation. Traditional commercial antifreeze agents like sugar and phosphates will bring sweet taste, high salt content, and high calorie, while organic solvents like glycerol and DMSO, can potentially have cytotoxic effects and cause irreversible damage to cells[7]. The present study attempts to express and produce a recombinant snow flea antifreeze peptide (rsfAFP) using B. subtilis (WB800N). The cryoprotective effect of rsfAFP on the physiological functions of Streptococcus thermophilus under freezing stress, and the mechanism by which rsfAFP interacts with these cells and ice were studied. Findings from this work will provide new insights into the mechanism by which rsfAFP regulates some cell physiological functions and the formation of ice crystals under freezing stress. Published in partnership with Beijing Technology and Business University antifreeze agent has great potential value in food processing and showed that the target protein was expressed by the WB800N storage
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