Nutritional and Volatile Characterisation of Milk Inoculated with Thermo-Tolerant Lactobacillus bulgaricus through Adaptive Laboratory Evolution

In this study, thermo-tolerant strain of ( ) was developed using gradual increase in temperature to induce Adaptive Laboratory Evolution (ALE). Viable colony count of 1.87 ± 0.98 log cfu/mL was achieved at 52 °C, using MRS agar supplemented with 2% lactose. Changes in bacteria morphology were discov...

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Bibliographic Details
Published in:Foods 2021-11, Vol.10 (12), p.2944
Main Authors: Liang, Jiahui, Yoo, Michelle Ji Yeon, Seale, Brent, Grazioli, Gianpaolo
Format: Article
Language:English
Subjects:
Acid production
adaptive laboratory evolution
Amino acids
Aroma
Bacteria
Cheese
Control rods
Dairy products
Diacetyl
Dilution
DNA fingerprinting
Enzymes
Evolution
Fermentation
Food science
Glycerol
Laboratories
Lactic acid
Lactobacilli
Lactobacillus bulgaricus
Lactose
Metabolomics
Methionine
Milk
Morphology
Probiotics
Proteolysis
Solid phase methods
Volatiles
Whey
Yogurt
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Summary:In this study, thermo-tolerant strain of ( ) was developed using gradual increase in temperature to induce Adaptive Laboratory Evolution (ALE). Viable colony count of 1.87 ± 0.98 log cfu/mL was achieved at 52 °C, using MRS agar supplemented with 2% lactose. Changes in bacteria morphology were discovered, from rod (control) to filament (52 °C) to cocci after frozen storage (-80 °C). When milk was inoculated with thermo-tolerant , lactic acid production was absent, leaving pH at 6.84 ± 0.13. This has caused weakening of the protein network, resulting in high whey separation and lower water-holding capacity (37.1 ± 0.35%) compared to the control (98.10 ± 0.60%). Significantly higher proteolytic activity was observed through free amino acids analysis by LC-MS. Arginine and methionine (237.24 ± 5.94 and 98.83 ± 1.78 µg/100 g, respectively) were found to be 115- and 275-fold higher than the control, contributing to changing the aroma similar to cheese. Further volatile analysis through SPME-GC-MS has confirmed significant increase in cheese-aroma volatiles compared to the control, with increase in diacetyl formation. Further work on DNA profiling, metabolomics and peptidomics will help to answer mechanisms behind the observed changes made in the study.
ISSN:2304-8158
2304-8158
DOI:10.3390/foods10122944