The colonial diameter of Lactococcus lactis spp. lactis isolates on MRS agar was promoted by providing negative atmospheric pressure and /or enrichment of negative atmosphere by CO2 gas in vacuum desiccator. In this study, application of negative atmospheric pressure or enrichment of negative atmosphere by CO2 gas at 722 mmHg was observed for maximum (2.5 mm) colony size of L. lactis spp. lactis on agar surface. No significant difference was observed in the colonial diameter in the presence of negative atmospheric pressure or enrichment of negative atmosphere by CO2 gas at 722 to 608 mmHg pressure.
Table of Contents
1. INTRODUCTION
2. MATERIALS AND METHODS
2.1 Samples
2.2 Bacterial strains and growth conditions
2.3 Identification
2.4 Effect of different levels of O2 and CO2 gases on colony formation
3. RESULTS AND DISCUSSION
4. CONCLUSION
Objectives and Research Themes
The primary objective of this study is to investigate how varying levels of oxygen and carbon dioxide, as well as different atmospheric pressures, affect the colony diameter of Lactococcus lactis spp. lactis isolates. The research addresses the challenge of optimizing laboratory cultivation conditions for this micro-aerophilic bacterium.
- Isolation and phenotypic identification of L. lactis spp. lactis from diverse dairy and non-dairy sources.
- Evaluation of the impact of negative atmospheric pressure on bacterial growth.
- Assessment of the role of CO2 enrichment in enhancing colonial diameter.
- Comparative analysis of different atmospheric pressures (ranging from 760 mmHg to 608 mmHg) on colony formation.
- Determination of optimal environmental conditions for the routine laboratory cultivation of the species.
Excerpt from the Book
INTRODUCTION
Lactococcus lactis is one of the beneficial and food grade microflora of dairy and food industry. Its four sub-species, L. lactis spp. cremoris, L. lactis spp. hordniae, L. lactis spp. lactis (including biovar diacetylactis) and L. lactis spp. tructae have since been recognized (Pérez et al., 2011). Amongst, L. lactis spp. lactis and spp. cremoris are widely important in dairy and food industry in manufacturing several kinds of chesses such as Cheddar, Monterey, Jack, Gouda, Edam, Muenster, Feta, Blue, Gorgonzola, Roquefort, Brie, Camembert, Havarti, Colby, Swiss, and Mozzarella, sour milk, butter milk, kefir, fermented sausages, cucumber pickles, sauerkraut and vegetable pickles (Salminen and Von Wright 1993; Vanniel and Hahn-Hagerdal 1999; Boonmee et al., 2003).
L. lactis is defined as Gram +ve, catalase –ve, homo-fermentative microaerophilic cocci (Samarzija et al., 2001). Being micro-aerophilic, L. lactis requires less O2 to grow well or develop colony on agar surface because oxygen has negative effect on the growth and survival of L. lactis (Duwat et al., 2001). Although having O2 tolerance capability, L. lactis is able to develop colony on agar surface of the diameter of ≤1mm. As a result, substantial interests exist in searching of some approaches which could increase the diameter of colony on agar surface of >1mm diameter.
Summary of Chapters
INTRODUCTION: This section provides an overview of the importance of L. lactis in the food industry, defines its biological characteristics as a microaerophilic bacterium, and identifies the need for methods to enhance its colonial growth.
MATERIALS AND METHODS: This chapter details the collection of samples from various dairy and non-dairy sources, the specific bacterial strains used, identification techniques, and the experimental setup involving vacuum desiccators to manipulate gas levels.
RESULTS AND DISCUSSION: This part presents the experimental data regarding the colony sizes observed under various oxygen and carbon dioxide levels, demonstrating that 722 mmHg is optimal for maximizing colonial diameter.
CONCLUSION: This section summarizes the study's findings, affirming that negative atmospheric pressure and CO2 enrichment are effective methods for increasing the surface growth of L. lactis spp. lactis for laboratory cultivation.
Keywords
Lactococcus lactis spp. lactis, O2 concentration, CO2 concentration, negative atmospheric pressure, colonial diameter, dairy microbiology, food grade microflora, microaerophilic, bacterial growth, vacuum desiccator, phenotypic identification, PCR-RFLP, agar surface, incubation, laboratory cultivation.
Frequently Asked Questions
What is the primary focus of this research?
The research focuses on identifying effective methods to increase the colony diameter of Lactococcus lactis spp. lactis on agar surfaces by modifying atmospheric conditions.
Which bacterial species were examined?
The study specifically examines Lactococcus lactis spp. lactis, with additional reference strains like Lactobacillus acidophilus and Lactobacillus brevis used for comparison.
What is the core research objective?
The objective is to find a way to overcome the growth limitation (≤1mm colony size) typically seen in L. lactis, aiming for diameters greater than 1mm through atmospheric adjustment.
What scientific methods were employed?
The study used phenotypic identification, litmus milk reduction tests, PCR amplification of the gad B gene, and RFLP assays, combined with controlled incubation under varying gas pressures in vacuum desiccators.
What does the main body of the paper cover?
The main body covers the isolation of strains from local dairy and non-dairy samples, the experimental manipulation of O2 and CO2 levels, and the observation of resulting colonial growth.
Which keywords best characterize this work?
Key concepts include Lactococcus lactis, negative atmospheric pressure, colonial diameter, and carbon dioxide enrichment.
Was there a difference in growth between different dairy samples?
Yes, the study identified that the highest number of L. lactis spp. lactis strains were isolated from cow milk, followed by buffalo milk, with no isolates found in vegetables or certain other sources.
Is there an optimal pressure identified for colony growth?
Yes, the study concluded that 722 mmHg is the optimal pressure for both O2 and CO2 to achieve maximum colony size (2.5 mm) for the tested strains.
Did the researchers observe significant differences between the gases?
The researchers noted that no significant stimulation was observed specifically between O2 and CO2 treatments when keeping the pressure within the 722 to 608 mmHg range; both provided similar enhancements compared to standard atmospheric conditions.
- Quote paper
- Priti Khemariya (Author), Sudhir Singh (Author), Gopal Nath (Author), Anil K. Gulati (Author), 2016, Effect of different levels of O2 and CO2 gases on the growth of Lactococcus lactis spp. lactis, Munich, GRIN Verlag, https://www.grin.com/document/316237
