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Direct bio-utilization of untreated rapeseed meal for effective iturin A production by Bacillus subtilis in submerged fermentation.

Jin H, Zhang X, Li K, Niu Y, Guo M, Hu C, Wan X, Gong Y, Huang F - PLoS ONE (2014)

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: Oil Crops Research Institute, Chinese Academy of Agriculture Sciences, Wuhan, China; Hubei Key Laboratory of Lipid Chemistry and Nutrition, Wuhan, China.

ABSTRACT
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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Time courses of pH and dissolved oxygen under different nitrogen sources during the entire fermentation process in bioreactor batch fermentation.A: rapeseed meal; B: peptone; C: ammonium nitrate; dot lines: Dissolved oxygen; bold lines: pH.
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pone-0111171-g005: Time courses of pH and dissolved oxygen under different nitrogen sources during the entire fermentation process in bioreactor batch fermentation.A: rapeseed meal; B: peptone; C: ammonium nitrate; dot lines: Dissolved oxygen; bold lines: pH.

Mentions: Currently, dissolved oxygen (DO) and pH are two conventional state variables for monitoring fermentative process, and to some extent, their changes reflect the metabolic characteristic of cells and may provide some useful information for industrial process control. The change modes of on-line pH and DO in batch fermentation under different nitrogen sources are shown in Figure 5. For all three batches, the aeration rate (2 vvm) and agitation speed (600 rpm) were held constant during the entire fermentation process. The actual pH was maintained automatically at approximately 7.0 by the addition of 4 mol/L NaOH and 4 mol/L H2SO4. Figure 5 indicates that DO and pH displayed different change tendencies when different nitrogen sources were used for iturin A production. When rapeseed meal was used, DO decreased to about 0% rapidly for the first 10 h and maintained almost constant until 55 h, indicating a high oxygen demand during this period. Further, DO began to rise gradually at 55 h with the depletion of available nutrients. On the other hand, pH was at the low limit for the first 12 h and then rose rapidly and was maintained at the high limit by continuous addition of acid solution till the cessation of fermentation (Figure 5A), indicating that alkali was added during the first 12 h and both acidic and alkali solutions were needed to maintain pH constant during the fermentation. When peptone was used as a nitrogen source, DO began to rise at 20 h, much earlier than that when using rapeseed as a nitrogen source (Figure 5B); moreover, the pH showed an intermittent change during fermentation: from the low limit (0–12 h), to the high limit (12–30 h), then to the low limit (30–50 h) again, and finally to the high limit (50–77 h). However, when inorganic ammonium nitrate was used as a nitrogen source, the sudden rise of pH and DO at 30 h was simultaneous, indicating that the available sugar was completely consumed at that time (Figure 5C and Figure 3C). In contrast to ammonium nitrate, using peptone and rapeseed meal protein as nitrogen sources might be used as a carbon source for iturin A synthesis when Bacillus subtilis suffered from carbon starvation. The differences in pH during the fermentation process may reflect different regulatory mechanisms of Bacillus subtilis in response to different nitrogen sources. The intermittent pattern of pH was only observed with strain grown on peptone and ammonium nitrate but not in rapeseed meal. The precise mechanism for this phenomenon remains elusive.


Direct bio-utilization of untreated rapeseed meal for effective iturin A production by Bacillus subtilis in submerged fermentation.

Jin H, Zhang X, Li K, Niu Y, Guo M, Hu C, Wan X, Gong Y, Huang F - PLoS ONE (2014)

Time courses of pH and dissolved oxygen under different nitrogen sources during the entire fermentation process in bioreactor batch fermentation.A: rapeseed meal; B: peptone; C: ammonium nitrate; dot lines: Dissolved oxygen; bold lines: pH.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4215929&req=5

pone-0111171-g005: Time courses of pH and dissolved oxygen under different nitrogen sources during the entire fermentation process in bioreactor batch fermentation.A: rapeseed meal; B: peptone; C: ammonium nitrate; dot lines: Dissolved oxygen; bold lines: pH.
Mentions: Currently, dissolved oxygen (DO) and pH are two conventional state variables for monitoring fermentative process, and to some extent, their changes reflect the metabolic characteristic of cells and may provide some useful information for industrial process control. The change modes of on-line pH and DO in batch fermentation under different nitrogen sources are shown in Figure 5. For all three batches, the aeration rate (2 vvm) and agitation speed (600 rpm) were held constant during the entire fermentation process. The actual pH was maintained automatically at approximately 7.0 by the addition of 4 mol/L NaOH and 4 mol/L H2SO4. Figure 5 indicates that DO and pH displayed different change tendencies when different nitrogen sources were used for iturin A production. When rapeseed meal was used, DO decreased to about 0% rapidly for the first 10 h and maintained almost constant until 55 h, indicating a high oxygen demand during this period. Further, DO began to rise gradually at 55 h with the depletion of available nutrients. On the other hand, pH was at the low limit for the first 12 h and then rose rapidly and was maintained at the high limit by continuous addition of acid solution till the cessation of fermentation (Figure 5A), indicating that alkali was added during the first 12 h and both acidic and alkali solutions were needed to maintain pH constant during the fermentation. When peptone was used as a nitrogen source, DO began to rise at 20 h, much earlier than that when using rapeseed as a nitrogen source (Figure 5B); moreover, the pH showed an intermittent change during fermentation: from the low limit (0–12 h), to the high limit (12–30 h), then to the low limit (30–50 h) again, and finally to the high limit (50–77 h). However, when inorganic ammonium nitrate was used as a nitrogen source, the sudden rise of pH and DO at 30 h was simultaneous, indicating that the available sugar was completely consumed at that time (Figure 5C and Figure 3C). In contrast to ammonium nitrate, using peptone and rapeseed meal protein as nitrogen sources might be used as a carbon source for iturin A synthesis when Bacillus subtilis suffered from carbon starvation. The differences in pH during the fermentation process may reflect different regulatory mechanisms of Bacillus subtilis in response to different nitrogen sources. The intermittent pattern of pH was only observed with strain grown on peptone and ammonium nitrate but not in rapeseed meal. The precise mechanism for this phenomenon remains elusive.

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: Oil Crops Research Institute, Chinese Academy of Agriculture Sciences, Wuhan, China; Hubei Key Laboratory of Lipid Chemistry and Nutrition, Wuhan, China.

ABSTRACT
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.

Show MeSH