Production of Bacillus thuringiensis‐based biopesticides in batch and fed batch cultures using wastewater sludge as a raw material

Abstract

Bacillus thuringiensis subsp kurstaki was grown in batch and fed batch cultures using wastewater sludge as a raw material. A simple fed batch strategy based on dissolved oxygen measurement during the fermentation cycle was developed in this work. It was established that while shifting the process strategy from batch to fed batch, the maximum spore concentration was increased from 5.62 × 10 8 to 8.6 × 10 8 colony forming units per cm 3 and resulted in an increase of entomocidal activity from 13 × 10 9 to 18 × 10 9 spruce budworm potency units per dm 3 . Higher entomotoxicity was recorded at low spore concentration using wastewater sludge as a raw material whereas low entomotoxicity was reported at high spore concentration in synthetic medium.

Oxygen supply in Bacillus thuringiensis fermentations: bringing new insights on their impact on sporulation and δ-endotoxin production

“…Furthermore, these high μ m values (around 1 h −1 ) showed that the cultures were not under any other nutritional or environmental limitation, including oxygen, during the first 4-5 h of fermentation, the time they were calculated. Similar or even smaller μ m values were previously described for other Bt strains under culture conditions that were not considered limiting for growth (Flores et al 1997;Rowe et al 2003;Yezza et al 2005;López-Y-López and De La Torre 2005). For all conditions evaluated, it was also observed that the exponential phase was followed by a period of non-exponential growth, where cell growth curves presented a linear profile.…”

“…Higher DO level also led to a positive impact on spore production (Table 1), which can be explained by increasing growth rates with the enhancement of DO concentrations. Fast growing cells carry higher energy, which leads to a higher sporulation (Yezza et al 2005). Quantitatively, the differences in spore counts are in agreement with those verified for Bti by Kraemer-Schafhalter and Moser (1996) using similar DO levels, but diverged from those obtained by Avignone-Rossa et al (1992), who found analogous spore counts with different DO values.…”

“…Earlier works demonstrated that in Bt cultures oxygen uptake rates are very high during the vegetative growth, falling drastically after the beginning of the transition phase and maintaining a decreasing profile until the end (Rowe et al 2003;Yezza et al 2005;Berbert-Molina et al 2008;Amicarelli et al 2010). Indeed, some authors verified that lower aeration rates in the sporulation phase, in relation to those employed in the earlier stages of growth, led to a greater toxicity in Btk cultures (Ghribi et al 2007a).…”

“…The main focus has been the optimization of process variables that lead to improvements in growth, sporulation, and toxin synthesis. Several culture media formulations, frequently based on low-cost substrates, have been proposed with this same purpose (Liu and Tzeng 2000;Saksinchai et al 2001;Yezza et al 2005;Ghribi et al 2007b). Additionally, there is evidence that process performance can be affected by the Bt subspecies or strain employed (Farrera et al 1998).…”

Anaerobic digested sludge: a new supplementary nutrient source for ethanol production

“…Thus, biotechnological products such as biopesticides (Yezza et al 2005), biochemicals such as lactic acid (Ma et al 2014), and biofuels such as biohydrogen (Ting and Lee 2007) have been produced using WAS as a nutrient source for the involved microorganisms. Cheung and Anderson (1997) tried to produce ethanol from the cellulose content of primary sludge of WWTPs, via simultaneous saccharification and fermentation (SSF).…”