Establishment of a rapeseed meal fermentation model for iturin A production by Bacillus amyloliquefaciens CX‐20

Abstract

Summary Iturin A is an important broad‐spectrum antifungal cyclic lipopeptide used as an ideal potential biological control agent. However, its application is limited mainly due to the producer strains’ low productivity and the high production costs. Here, a potentially industrial strain Bacillus amyloliquefaciens CX‐20 was proved to use low‐cost rapeseed meal (RSM) as the sole source of all nutrients except the carbon source for the high productivity of iturin A. A fermentation model was first established to analyse the specific roles of different RSM components on iturin A production. Proteins and minerals in RSM were confirmed to play positive role, whereas fibre had negative effect. And the maximal concentration of iturin A was predicted to be more than 1.64 g l−1 by the established evaluation model. Moreover, submerged fermentation of B. amyloliquefaciens CX‐20 demonstrated a strong ability to hydrolyse RSM and release water‐soluble nutrients. This fermentation broth, a mixture of Bacillus, iturin A and RSM hydrolysate, could simultaneously combat clubroot disease and promote the growth of Brassica napus. In conclusion, this study provides a promising strategy to achieve full utilization of RSM for the production of a combination of value‐added biological control agent and biofertilizer.

The unconventional adverse effects of fungal pretreatment on iturin A fermentation by Bacillus amyloliquefaciens CX‐20

“…Iturin A is an important antifungal cyclic lipopeptide with wide application prospects. In previous studies, we verified the advantages of direct bio-utilization of untreated RSM for effective iturin A production by Bacillus in submerged fermentation, which compared favourably with commercial nitrogen sources (Jin et al, 2014(Jin et al, , 2015Chen et al, 2019a). Moreover, the potential industrial strain B. amyloliquefaciens CX-20 was able to achieve high iturin A productivity by directly using RSM for all nutrients except for the carbon source (Chen et al, 2019a).…”

“…(2014) and Chen et al . (2019a), which demonstrated that almost no iturin A were produced when 8 g l −1 ammonium nitrate was used as the nitrogen source. However, when an equal amount of ammonium nitrate was added into RSM medium, the yield of iturin A reached 1.07 g l −1 in spite of the negative effects of ammonium nitrate (Fig.…”

“…In previous studies, we verified the advantages of direct bio‐utilization of untreated RSM for effective iturin A production by Bacillus in submerged fermentation, which compared favourably with commercial nitrogen sources (Jin et al, 2014, 2015; Chen et al ., 2019a). Moreover, the potential industrial strain B. amyloliquefaciens CX‐20 was able to achieve high iturin A productivity by directly using RSM for all nutrients except for the carbon source (Chen et al ., 2019a). Even though it was not optimal, when glucose was used as the carbon source, the maximum production of iturin A by B. amyloliquefaciens CX‐20 after 72 h of batch fermentation in shake flasks reached up to 1.25 g l −1 .…”

“…This value corresponded to a yield of 13.89 g iturin A per kg RSM, which was very close to the highest production level reported to date. This previous record of 14 g iturin A per kg dry substrate was obtained using B. subtilis RB14‐CS in a medium based on soybean curd residue (Mizumoto et al ., 2007; Chen et al ., 2019a). However, whether fungal pretreatment can further improve the synthesis of iturin A is still unknown.…”

Simultaneous hydrolysis with lipase and fermentation of rapeseed cake for iturin A production by Bacillus amyloliquefaciens CX-20

“…Iturin A was extracted according to a reported method [4, 5, 24]. Briefly, 0.3 mL of the mixed fermentation broth was added into a 2 mL glass tube containing 1.2 mL of methanol, shaken well and incubated for 60 min.…”