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Challenges for mass production of nematodes in submerged culture
1Departamento de Biotecnología y Bioingeniería, Centro de Investigación y de Estudios Avanzados del IPN, PO Box 14-740, 07000, México DF, Mexico. mmdelato@mail.cinvestav.mx
Abstract:
Nematodes of Steinernema and Heterorhabditis genera are used as agents in insect biocontrol programs. They are associated with specific bacteria which are also involved in the mechanism of pathogenicity and which are consumed by nematodes as living food. S. feltiae has various developmental stages in its life cycle, including four juvenile stages, adults and the free living form. During mating, males coil themselves around the female, which is around 1 cm long. Successful commercialization of nematode-bacteria biocontrol products depends on the ability to produce sufficient quantities of these products at competitive prices for a full pest control program. This could be feasible if high cell density submerged cultures are designed and implemented; however, major problems related to nematodes mass production in a bioreactor remain unsolved due to the lack of knowledge about the physiological aspects of the nematode, bacteria and nematode-bacteria association, interaction between the three phases present in the bioreactor (liquid, gas, nematodes-bacteria), possibility of mating under hydrodynamic stress conditions, etc. We have found that the two most important engineering aspects to take into account the mass propagation of nematodes are oxygen transfer rate and hydrodynamics to allow mating and to avoid mechanical damage of juveniles in stage 2. This article focuses on several aspects related to the fermentation system such as kinetics of growth, shear stress, hydrodynamics fields in the bioreactor and oxygen demand. Also, results published by other groups, together with those of our own, will be discussed in relation to the main challenges found during the fermentation process.
Insights
Mass-producing beneficial nematodes for biocontrol requires optimizing bioreactor conditions. Key engineering factors for successful nematode propagation include managing oxygen transfer and hydrodynamics to facilitate mating and prevent damage.
Area of Science:
- Biotechnology
- Entomology
- Microbial Fermentation
Background:
- Nematodes from the Steinernema and Heterorhabditis genera, along with their symbiotic bacteria, are crucial for biological insect control.
- Commercial viability of these biocontrol agents hinges on efficient, large-scale production methods.
- Current mass production in bioreactors faces challenges due to limited understanding of nematode physiology and interactions within the fermentation system.
Purpose of the Study:
- To identify critical engineering parameters for optimizing the mass propagation of entomopathogenic nematodes in submerged cultures.
- To investigate the influence of oxygen transfer rate and hydrodynamics on nematode mating and survival during fermentation.
- To analyze fermentation system aspects including growth kinetics, shear stress, and oxygen demand.
Main Methods:
- Focus on engineering aspects of bioreactor design and operation for nematode mass culture.
- Analysis of hydrodynamics, oxygen transfer rates, and shear stress within the bioreactor.
- Review of existing literature and presentation of novel findings on nematode fermentation challenges.
Main Results:
- Oxygen transfer rate and hydrodynamics are identified as the most critical engineering factors for nematode mass propagation.
- Proper management of these factors is essential for enabling nematode mating and preventing mechanical damage to infective juveniles (J2).
- Understanding growth kinetics and oxygen demand is vital for successful fermentation system design.
Conclusions:
- Successful commercialization of nematode-bacteria biocontrol products is achievable through optimized high-cell-density submerged cultures.
- Addressing engineering challenges related to oxygen transfer and hydrodynamics is paramount for overcoming current mass production limitations.
- Further research into the physiological and interactive aspects of nematodes and bacteria in bioreactors will enhance biocontrol agent production.
