Direct Bio-Utilization of Untreated Rapeseed Meal for Effective Iturin A Production by Bacillus subtilis in Submerged Fermentation
et al. (2014) Direct Bio-Utilization of Untreated Rapeseed Meal for Effective Iturin A Production by Bacillus subtilis in
Submerged Fermentation. PLoS ONE 9(10): e111171. doi:10.1371/journal.pone.0111171
Direct Bio-Utilization of Untreated Rapeseed Meal for Effective Iturin A Production by Bacillus subtilis in Submerged Fermentation
Hu Jin 0
Xinran Zhang 0
Kunpeng Li 0
Yanxing Niu 0
Mian Guo 0
Chuanjiong Hu 0
Xia Wan 0
Yangmin Gong 0
Fenghong Huang 0
Jonathan A. Coles, Glasgow University, United Kingdom
0 1 Oil Crops Research Institute, Chinese Academy of Agriculture Sciences , Wuhan , China , 2 Hubei Key Laboratory of Lipid Chemistry and Nutrition , Wuhan , China , 3 College of Life Science, Hubei University , Wuhan , China
The feasibility of using untreated rapeseed meal as a nitrogen source for iturin A production by Bacillus subtilis 3-10 in submerged fermentation was first evaluated by comparison with two different commercial nitrogen sources of peptone and ammonium nitrate. A significant promoting effect of rapeseed meal on iturin A production was observed and the maximum iturin A concentration of 0.60 g/L was reached at 70 h, which was 20% and 8.0 fold higher than that produced from peptone and ammonium nitrate media, respectively. It was shown that rapeseed meal had a positive induction effect on protease secretion, contributing to the release of soluble protein from low water solubility solid rapeseed meal for an effective supply of available nitrogen during fermentation. Moreover, compared to raw rapeseed meal, the remaining residue following fermentation could be used as a more suitable supplementary protein source for animal feed because of the great decrease of major anti-nutritional components including sinapine, glucosinolate and its degradation products of isothiocyanate and oxazolidine thione. The results obtained from this study demonstrate the potential of direct utilization of low cost rapeseed meal as a nitrogen source for commercial production of iturin A and other secondary metabolites by Bacillus subtilis.
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Funding: This work was supported by the National Natural Science Foundation of China (No. 31201461), National High-tech R&D Program of China (863
Program, No. 2011AA100904), National Key Technology Research and Development Program (No. 2012BAD49G00), and Director Fund of Oil Crops Research
Institute (Nos. 1610172014006, 1610172013005). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the
manuscript.
Competing Interests: The authors have declared that no competing interests exist.
The increasing demand for a steady, healthy food supply
requires an efficient control of major plant pests and diseases [1].
Currently, conventional crop management practices are based
largely on the application of synthetic pesticides, which have
caused serious environmental and health problems. Moreover, the
efficacy of synthetic pesticides is gradually decreasing due to the
adaptation and resistance of pathogens to these pesticides [2]. One
of the greatest ecological challenges in the near future is to develop
environmentally friendly alternatives [3]. Recently, biological
control agents have received considerable attention as alternatives
to chemical pesticides for plant diseases and are considered to be
one of the most promising methods for rational and safe
cropmanagement practices [4]. Bacillus subtilis, one of the most
commonly used and well-studied microbial species, has the
potential to produce more than two dozen structurally diverse
antimicrobial compounds with broad inhibitory spectrum and
high viability [5]. Among these antimicrobial compounds, cyclic
lipopeptides of iturin, surfactin and fengycin families have
wellrecognized potential uses in biotechnology and biopharmaceutical
applications because of their excellent surfactant properties.
Iturin A is a cyclic lipopeptide antibiotic with the structure of a
cyclic heptapeptide linked to a 1417 carbons b-amino fatty acid
chain [3]. This special structure endows it with strong antifungal
action because of its membrane permeable properties [6]. It is a
potential weapon for controlling plant diseases caused by
phytopathogenic fungi. However, a significant obstacle to
largescale industrial application of cyclic lipopeptide antibiotics such as
iturin A is the high production cost coupled with a low production
rate. If the production costs of these cyclic lipopeptide antibiotics
become competitive with the synthetic chemical pesticides, their
industrial use might be expected to grow tremendously in the
coming decade [7]. In order to achieve this goal, recent efforts
have been focused on the reduction of lipopeptide antibiotics
production costs through improving the yield and utilization of
low-cost feedstocks, such as soybean curd residue [8], soybean and
sweet potato residues [9], cassava flour wastewater [10,11],
synthetic wastewater [12] and waste soybean oil [13]. However,
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