Development of a cost-effective medium for Photorhabdus temperata bioinsecticide production from wastewater and exploration of performance kinetic

Sahar Keskes,Slim Tounsi,Emna Sahli,Imen Ben Atitallah,Wafa Jallouli,Mohamed Chamkha,Fatma Driss

doi:10.1038/s41598-020-80773-5

Sahar Keskes, Slim Tounsi + Show 5 more

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https://doi.org/10.1038/s41598-020-80773-5

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Abstract

This study investigates the optimization of the culture conditions for enhancing Photorhabdus temperata biopesticide production using wastewater (WS4) as a raw material. Box-Behnken design (BBD) was used to evaluate the effects of carbon to nitrogen ratio (C/N), sodium chloride concentration and inoculum size on P. temperata biomass production and insecticidal activity. For an enhanced biopesticide production, the optimum operating conditions were as follows: inoculum size = 4%; C/N ratio = 12.5 and [NaCl] = 4 g/L for two responses. 1.95 and 2.75 fold improvements in oral toxicity and biomass production were respectively obtained in the cost-effective medium developed in this study (WS4 I) using the three variables at their optimal values. Under the optimized conditions, WS4 I-grown cells exhibited higher membrane integrity according to flow cytometry analysis since dead cells presented only 9.2% compared to 29.2% in WS4. From batch fermentations carried out in WS4 I and WS4, P. temperata kinetic parameters in terms of biomass production and substrate consumption rates were modeled. The obtained results showed that the maximum specific growth rate in WS4 I was of 0.43 h−1 while that obtained in WS4 was of 0.14 h−1. In addition, the efficiency of P. temperata to metabolize organic carbon was enhanced by optimizing the culture conditions. It reached 72.66% instead of 46.18% in the control fermentation after 10 h of incubation. Under the optimized conditions, P. temperata cells showed the highest specific consumption rate resulting in a toxin synthesis improvement.

Highlights

This study investigates the optimization of the culture conditions for enhancing Photorhabdus temperata biopesticide production using wastewater (WS4) as a raw material
The improvement of P. temperata biomass production was well studied in two media: the optimized medium (OM)[14] based on glucose and yeast extract and the complex medium (CM)[15] based on soya bean meal, but it was never reported in wastewater
All results related to the determination of Total solids (TS), total organic carbon (TOC) concentration and bioassays were the average of three replicates of three separate experiments

Summary

Introduction

This study investigates the optimization of the culture conditions for enhancing Photorhabdus temperata biopesticide production using wastewater (WS4) as a raw material. Considerable success has been made through the use of Photorhabdus as bioinsecticide against different insect orders at a lab scale, the development of low-cost P. temperata biopesticide remains a challenge for the industrial production of this bacterium. In this context, a Tunisian industrial wastewater (WS4) has been evaluated for a potential application of low-cost feedstock. A Tunisian industrial wastewater (WS4) has been evaluated for a potential application of low-cost feedstock In this medium, low P. temperata biomass production and oral toxicity against E. kuehniella were obtained, which were of 4 × 108 cells/mL and 42%, respectively[13]. Maintaining glucose at 4 g/L in the OM significantly increased P. temperata biomass p roduction[16]

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