The present study deals with the batch and fed-batch mass production of Steinernema carpocapsae. S. carpocapsae is an entomoparasitic nematode that is used as a biological control agent of soil-borne crop insect pests. The ability and efficiency of fed-batch culture process was successful through the utilization of the nematode’s bacterial symbiont Xenorhabdus nematophila. Results from the fed-batch process were compared to those obtain from the standard batch process. The fed-batch process successively improved the mass production process of S. carpocapsae employing liquid medium technology. Within the first week of the fed-batch process (day six), the nematode density obtained was 202,000 nematodes mL−1; whereas on day six, batch culture mode resulted in a nematode density of 23,000 nematodes mL−1. The fed-batch process was superior to that of batch production with a yield approximately 8.8-fold higher. In fed-batch process, the nematode yield was improved 88.6 % higher within a short amount of time compared to the batch process. Fed-batch seems to make the process more efficient and possibly economically viable.
Heterorhabditis bacteriophora and Steinernema carpocapsae are microscopic entomoparasitic nematodes (EPNs) that are attractive, organic alternatives for controlling a wide range of crop insect pests. EPNs evolved with parasitic adaptations that enable them to "feast" upon insect hosts. The infective juvenile, a non-feeding, developmentally arrested nematode stage, is destined to seek out insect hosts and initiates parasitism. After an insect host is located, EPNs enter the insect body through natural openings or by cuticle penetration. Upon access to the insect hemolymph, bacterial symbionts (Photorhabdus luminescens for H. bacteriophora and Xenorhabdus nematophila for S. carpocapsae) are regurgitated from the nematode gut and rapidly proliferate. During population growth, bacterial symbionts secrete numerous toxins and degradative enzymes that exterminate and bioconvert the host insect. During development and reproduction, EPNs obtain their nutrition by feeding upon both the bioconverted host and proliferated symbiont. Throughout the EPN life cycle, similar characteristics are seen. In general, EPNs are analogous to each other by the fact that their life cycle consists of five stages of development. Furthermore, reproduction is much more complex and varies between genera and species. In other words, infective juveniles of S. carpocapsae are destined to become males and females, whereas H. bacteriophora develop into hermaphrodites that produce subsequent generations of males and females. Other differences include insect host range, population growth rates, specificity of bacterial phase variants, etc. This review attempts to compare EPNs, their bacterial counterparts and symbiotic relationships for further enhancement of mass producing EPNs in liquid media.
Steinernema carpocapsae is a microscopic entomopathogenic nematode (EPN) that may be used as an alternative to chemical pesticide. This species creates a symbiotic relationship with the bacteria Xenorhabdus nematophila. This biological control agent has many advantages compared to chemical pesticides as it does not harm either the environment or humans. Steinernema carpocapsae is a vector for the bacteria to infect the targeted insect pest. The bacteria kills the host within 24-48 hours. This paper focuses on the mass production of beneficial nematodes using solid state fermentation. The purpose of the experiment was to find the optimum conditions to mass produce the nematode efficiently. Maximizing yield with the minimalized nutrients will increase the cost efficiency of production, making it a more affordable attractive alternative to harmful chemical pesticides.
Xenorhabdus nematophila, an entomopathogenic bacterium that symbiotically associates with the entomoparasitic nematode Steinernema carpocapsae, was studied to determine its physiological parameters of glucose utilization. X. nematophila was cultured in chemically defined media containing various concentrations of glucose under optimal conditions utilizing a two-liter fermentation system. Specific growth rates were obtained from each glucose batch. Specific growth rates and their associated glucose concentrations were used to determine physiological parameters. These parameters include the bacterium's substrate utilization constant (K s) and its maximum specific growth rate (μ max). The bacteria exhibited a K s value of 2.02 mg/L suggesting that X. nematophila has a high affinity for glucose. The μ max of Xenorhabdus was determined to be 1.03 h−1. Further research is needed to determine if microbial affinities to different substrates have any influence on biological relationships (symbiosis, pathogenicity, parasitism, etc.) between prokaryotes and higher organisms.
A B S T R A C TEntomopathogenic nematodes (in the genus Steinernema and Heterorhabditis) have been studied and successfully commercialized as biological control agents. These organisms are highly virulent and safe for the non-target environment, animals and humans. For at least 200 target species, the nematode-bacteria complex has the potential to become a mass-marketed agricultural biopesticide. However, before nematodes can be successfully integrated into the agricultural system as a regular-use, "go-to" biopesticide, it is necessary to develop economical manufacturing processes. There are several manufacturing platforms: in vitro solid fermentation; in vitro liquid fermentation; and in vivo production. This review presents an analysis of each approach and discusses the advantages and disadvantages relative to the cost of production, technical expertise required, and quality of the final product.
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