Influence of temperature, pH and NaCl concentration on the maximal growth rate of Brochothrix thermosphacta and a bioprotective bacteria Lactococcus piscium CNCM I-4031

Abstract

The maximum specific growth rate (μ max) of Brochothrix thermosphacta, a spoilage bacteria of cooked peeled shrimp, and Lactococcus piscium CNCM I-4031, a bioprotective strain, was investigated under different conditions of temperature, NaCl concentrations and pH. The basic modelling approach used was the Gamma concept (γ-concept) and the model developed was then adapted to shrimp. Cardinal growth parameters were quite similar for the two strains, except for NaCl. No NaCl was required for growth and the NaCl max was three-times higher for B. thermosphacta than for L. piscium (62 and 23 g l −1 respectively). However, tolerance to NaCl was higher in seafood than in liquid broth, possibly due to presence of osmoltically active molecules. L. piscium and B. thermosphacta were psychrotolerant, with T min = −4.8 and −3.4 °C, T opt = 23.4 and 27.0 °C and T max = 27.2 and 30.8 °C respectively. The optimal pH was neutral and growth possible till pH = 4.8 for the two strains, assuming possible applications of the bioprotective strain in lightly marinated seafood. The μ max of B. thermosphacta in shrimp was a little higher than in L. piscium whatever the environmental conditions. Validation of the model showed that the γ-concept was suitable for predicting μ max of B. thermosphacta in shrimp. Data generated in this study can be used to adapt the model to other foods with few additional experiments and the effect of different parameters may be added in the future. The model was less accurate for the bioprotective strain and the effect of NaCl must be studied in more detail directly in the matrix. Highlights ► Effect of pH, temperature and NaCl on Lactococcus piscium has been modelled. ► Same work was performed on Brochothrix thermosphacta and data validated in shrimp. ► Cardinal values were closed except NaCl max (3 times higher for B. thermosphacta). ► B. thermosphacta grew faster in shrimp than L. piscium. ► Bioprotective effect of L. piscium is not due to a better adaptation to shrimp matrix.

Primary and secondary modeling of Brochothrix thermosphacta growth under different temperature and ph values

“…This same relationship was observed by Koutsoumanis et al (2006) in a study with fresh ground beef with pH ranging between 5.34 and 6.13 and stored at different temperatures (0-20 °C). Similarly Leroi et al (2012) in a study with different strains of B. thermosphacta observed increase in μmax. with the temperature rise (10-35 °C) and also with increasing pH 4.8 to around 7.0, above this value was noted to drop in μmax.…”

“…Generally, the pH closer the pH neutral, faster will be microbial growth. Leroi et al (2012) highlight in their work the neutral pH was great for the growth of B. thermosphacta, but its development was possible even in pH 4.8. Corroborating Gribble et al (2014) which points out that under aerobic conditions B. thermosphacta is able to grow at low pH.…”

Treatment of chromium contaminated soil using bioremediation

“…pH is one of the factor that influence bacterial growth. Chromium removal process can run optimally at the optimum pH for bacterial growth [14]. G. Cheng and X. Li.…”

“…Temperature is a factor that affects the process of chromium removal by bacteria. The optimum temperature of bacteria growth causes chromium removal to run maximally because the bacterial metabolism goes well [14]. Bacillus subtilis is mesophilic bacteria that has an optimum growth temperature ranged from 20 to 40 o C. The results of temperature measurements on all reactors (Fig.…”

The adverse effect of disrupted water-borne bacteria cells on flotation

“…Bacteria can exist in these water sources as intact cells which maintain their structural intactness, either viable or dead. Bacterial growth is sensitive to a range of physical, chemical and biological factors in the surrounding environment, with different optimal conditions for different types of bacteria (Adamberg et al, 2003;Leroi et al, 2012). When the surrounding conditions are beyond the range that a bacterial cell can grow, intact cells undergo cell disruption or cellular breakdown, a process called bacterial lysis (Geciova et al, 2002;Lewis, 2000).…”