Simulation modelling of bacterial growth in yoghurt

Area of Science:

• Microbiology
• Food Science
• Computational Biology

Background:

• Yoghurt production relies on the symbiotic fermentation by Streptococcus salivarius subsp. thermophilus and Lactobacillus delbrueckii subsp. bulgaricus.
• Bacterial cell shape and size can influence growth dynamics and metabolic efficiency during fermentation.

Purpose of the Study:

• To investigate the impact of Streptococcus salivarius subsp. thermophilus and Lactobacillus delbrueckii subsp. bulgaricus cell geometry and metabolism on yoghurt processing.
• To validate simulation results against experimental data for yoghurt fermentation.

Main Methods:

• Utilized INDISIM, an individual-based simulator, to model bacterial growth.
• Conducted two simulation sets: one focusing on geometry-driven differences and another incorporating metabolic variations in a simplified yoghurt model.

Main Results:

• In optimal conditions, Streptococcus salivarius subsp. thermophilus exhibited greater biomass growth than Lactobacillus delbrueckii subsp. bulgaricus, potentially due to its higher mass-to-surface ratio.
• Simulation results showed good qualitative agreement with experimental data.
• Inhibiting amino acid uptake in Streptococcus salivarius subsp. thermophilus emphasized the critical role of lactic acid in yoghurt processing.

Conclusions:

• Bacterial cell shape and size are significant factors influencing Streptococcus salivarius subsp. thermophilus and Lactobacillus delbrueckii subsp. bulgaricus growth in yoghurt.
• The INDISIM model provides a valuable tool for understanding and optimizing yoghurt fermentation processes.
• Lactic acid plays a crucial role in the overall dynamics of yoghurt production.