Machine learning predicts and provides insights into milk acidification rates of Lactococcus lactis

PLoS One. 2021 Mar 15;16(3):e0246287. doi: 10.1371/journal.pone.0246287. eCollection 2021.

Abstract

Lactococcus lactis strains are important components in industrial starter cultures for cheese manufacturing. They have many strain-dependent properties, which affect the final product. Here, we explored the use of machine learning to create systematic, high-throughput screening methods for these properties. Fast acidification of milk is such a strain-dependent property. To predict the maximum hourly acidification rate (Vmax), we trained Random Forest (RF) models on four different genomic representations: Presence/absence of gene families, counts of Pfam domains, the 8 nucleotide long subsequences of their DNA (8-mers), and the 9 nucleotide long subsequences of their DNA (9-mers). Vmax was measured at different temperatures, volumes, and in the presence or absence of yeast extract. These conditions were added as features in each RF model. The four models were trained on 257 strains, and the correlation between the measured Vmax and the predicted Vmax was evaluated with Pearson Correlation Coefficients (PC) on a separate dataset of 85 strains. The models all had high PC scores: 0.83 (gene presence/absence model), 0.84 (Pfam domain model), 0.76 (8-mer model), and 0.85 (9-mer model). The models all based their predictions on relevant genetic features and showed consensus on systems for lactose metabolism, degradation of casein, and pH stress response. Each model also predicted a set of features not found by the other models.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Computer Simulation
  • Food Microbiology
  • Genome, Bacterial
  • High-Throughput Screening Assays / methods*
  • Hydrogen-Ion Concentration
  • Lactococcus lactis / genetics
  • Lactococcus lactis / physiology*
  • Machine Learning
  • Milk / chemistry*
  • Milk / microbiology
  • Models, Theoretical
  • Whole Genome Sequencing

Grants and funding

SK acknowledges financial support from Innovation Fund Denmark (IFD), case no. 7038-00250B, www.innovationsfonden.dk. IFD had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Chr. Hansen A/S provided support in the form of salaries for authors SK, TV, GO, VP, GH, and JB and provided a pre-existing dataset, but did not have any additional role in the study design, analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘author contributions’ section.