Entomoparasitic nematodes (EPNs) are being commercialized as a biocontrol measure for crop insect pests, as they provide advantages over common chemical insecticides. Mass production of these nematodes in liquid media has become a major challenge for commercialization. Producers are not willing to share the trade secrets of mass production and by doing so, have made culturing EPNs extremely difficult to advance existing technologies. Theoretically, mass production in liquid media is an ideal culturing method as it increases cost efficiency and nematode quantity. This paper will review current culturing methodologies and suggest basic culturing parameters for mass production. This review is focused on Heterorhabditis bacteriophora; however, this information can be useful for other nematode species.

The study of growth of Lactococcus lactis NCIM 2114, a nisin producer, was modeled using continuously generated concentration data for growth in fermenter. The sigmoidal growth functions, Logistic, Gompertz, and Richards were used to fit the data. A nonlinear regression method was used to fit the data and estimate growth parameter values of L. lactis, using Marquardt algorithm with Statistical Software SPSS, version 20. Bacterial growth data from the exponential phase of the bacteria's growth was analyzed. An F test showed that the Gompertz and Logistic functions were acceptable 92% and 67% of times respectively in the batch fermenter runs where this particular application was used to derive the lag time, growth rates, and time to maximum growth rates of L. lactis. The maximal specific growth rate ranged between 0.23 h −1 to 0.30 h −1 and the lag time lasted up to a maximum of 1.63 h depending upon aeration conditions provided to the organism. This study will help to estimate specific growth rates and lag time of L. lactis under different growth conditions. Predicted values can be accurately determined.

No abstract

Photorhabdus luminescens, a bacterial symbiont of entomoparasitic nematodes, was cultured in a 10 L bioreactor. Cellular density and bioluminescence were recorded and volumetric oxygen transfer coefficient (k L a) and specific oxygen transfer rates were determined during the batch process. Exponential phase of the bacterium lasted for 20 h, showing a maximum specific growth rate of 0.339 h −1 in a defined medium. Bioluminescence peaked within 21h, and was maintained until the end of the batch process (48 h). The specific oxygen uptake rate (SOUR) was high during both lag and early exponential phase, and eventually reached a stable value of 0.33 mmol g −1 h −1 during stationary phase. Maintenance of 200 rpm agitation and 1.4 volume of air per volume of medium per minute (vvm) aeration, gave rise to a k L a value of 39.5 h −1 . This k L a value was sufficient to meet the oxygen demand of 14.4 g L −1 (DCW) biomass. This research is particularly relevant since there are no reports available on SOURs of symbiotic bacteria or their nematode partners. The insight gained through this study will be useful during the development of a submerged monoxenic culture of Heterorhabditis bacteriophora and its symbiotic bacterium P. luminescens in bioreactors.

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.