Kuliah Satuan Proses, Kinetika Pertumbuhan Mikroba

Summary

This lecture covers the basics of microbial growth kinetics, emphasizing methods to measure microbial growth such as viable cell count, filtration, microscopic count, and indirect methods like turbidity and metabolic activity. Key topics include the calculation of growth parameters like the specific growth rate, substrate affinity, and the impact of growth inhibitors. The lecture also explores the effect of environmental conditions, nutrient availability, and metabolic processes on microbial growth. Various formulas and models are presented, illustrating the relationship between biomass, substrate usage, and growth rate, providing essential insights into microbial growth dynamics.

Takeaways

• 😀 Microbial growth kinetics refers to the speed at which microbial populations grow, measured in terms of concentration changes over time.
• 😀 There are several methods to measure microbial growth, including viable cell count, filtration, most probable number (MPN), direct microscopic count, and indirect methods like turbidity or metabolic activity.
• 😀 The plate count method involves serial dilution of microbial samples to obtain countable colonies, simplifying the estimation of microbial population.
• 😀 Filtration is used for samples with low microbial numbers, where microorganisms pass through a filter and can be counted based on the number of colonies formed.
• 😀 The MPN method is used for heterogeneous samples like soil or water, relying on serial dilution and probability to estimate microbial numbers.
• 😀 Direct microscopic count is used to count microbial cells directly under a microscope, providing an immediate count of cells in a sample.
• 😀 Indirect methods for measuring microbial growth include turbidity measurement, metabolic activity assessment, and dry weight determination.
• 😀 Turbidity is measured by the amount of light absorbed or transmitted through a sample, with more microbial cells leading to greater light absorption.
• 😀 Metabolic activity can be used to estimate microbial growth by measuring products like carbon dioxide or acids produced by the microbes.
• 😀 Growth rate is influenced by environmental factors, energy sources, inhibitors, and the specific requirements of the microorganism being studied.
• 😀 The specific growth rate is the rate at which microbial biomass increases over time, and is calculated using mathematical models involving biomass and time changes.

Q & A

What is meant by microbial growth kinetics?

Microbial growth kinetics refers to the study of the rate of microbial growth, focusing on how the concentration or amount of microorganisms changes over time. It helps in understanding the speed at which microbes grow in a given environment.

What are the common methods to calculate microbial growth?

The common methods to calculate microbial growth include: 1) Plate count (or viable cell count), 2) Filtration method, 3) Most Probable Number (MPN), 4) Microscopic area count, and 5) Indirect methods such as turbidity measurement, metabolic activity, and dry weight analysis.

What is the plate count method in microbial growth calculation?

The plate count method involves serial dilution of a microbial sample, followed by plating on a petri dish. After incubation, colonies are counted to determine the concentration of microorganisms in the original sample.

How does the filtration method work for microbial growth calculation?

The filtration method is used when microbial numbers are low. The sample is passed through a filter that retains the microorganisms. The filter is then examined, and the number of colonies is counted to estimate the concentration of microorganisms.

What is the Most Probable Number (MPN) method?

The MPN method is used to estimate the number of viable microorganisms in a sample, typically for heterogeneous samples. It relies on serial dilutions and the probability of microbial growth at different dilution levels to estimate the concentration of microorganisms.

What are the advantages of the microscopic count method?

The microscopic count method directly counts the number of microbial cells observed under a microscope, allowing for a quick assessment of cell numbers without the need for culturing or incubation. However, it doesn't differentiate between dead and live cells.

What is the basic principle behind the turbidity method?

The turbidity method involves measuring the reduction in light transmission through a microbial culture. As the number of microbial cells increases, the turbidity increases, reducing the amount of light that passes through. This is directly proportional to the concentration of microorganisms.

What is metabolic activity as an indirect method for measuring microbial growth?

Metabolic activity measures the by-products of microbial metabolism, such as CO2 or acids. The presence and quantity of these products help estimate the number of microorganisms in the sample, providing an indirect measurement of growth.

How does the dry weight method help in calculating microbial growth?

The dry weight method involves filtering or centrifuging microbial cultures to separate the biomass from the medium. The biomass is then dried, and its weight is measured. This method is useful for measuring the growth of filamentous fungi but doesn't differentiate between living and dead cells.

What factors influence microbial growth rate?

Microbial growth rate is influenced by several factors, including the availability of nutrients, environmental conditions, temperature, pH, the presence of inhibitors, and the specific growth requirements of the microorganisms.