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

Wenchao Chen,Xuli Ma,Fenghong Huang,Minmin Yang,Xuan Li,Shouwen Chen,Xia Wan,Yanping Kang

doi:10.1186/s12896-019-0591-x

Wenchao Chen, Xuli Ma + Show 6 more

Open Access

https://doi.org/10.1186/s12896-019-0591-x

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Abstract

BackgroundRapeseed cake (RSC), as the intermediate by-product of oil extraction from the seeds of Brassica napus, can be converted into rapeseed meal (RSM) by solvent extraction to remove oil. However, compared with RSM, RSC has been rarely used as a raw material for microbial fermentation, although both RSC and RSM are mainly composed of proteins, carbohydrates and minerals. In this study, we investigated the feasibility of using untreated low-cost RSC as nitrogen source to produce the valuable cyclic lipopeptide antibiotic iturin A using Bacillus amyloliquefaciens CX-20 in submerged fermentation. Especially, the effect of oil in RSC on iturin A production and the possibility of using lipases to improve the iturin A production were analyzed in batch fermentation.ResultsThe maximum production of iturin A was 0.82 g/L at the optimal initial RSC and glucose concentrations of 90 and 60 g/L, respectively. When RSC was substituted with RSM as nitrogen source based on equal protein content, the final concentration of iturin A was improved to 0.95 g/L. The production of iturin A was further increased by the addition of different lipase concentrations from 0.1 to 5 U/mL into the RSC medium for simultaneous hydrolysis and fermentation. At the optimal lipase concentration of 0.5 U/mL, the maximal production of iturin A reached 1.14 g/L, which was 38.15% higher than that without any lipase supplement. Although rapeseed oil and lipase were firstly shown to have negative effects on iturin A production, and the effect would be greater if the concentration of either was increased, their respective negative effects were reduced when used together.ConclusionsAppropriate relative concentrations of lipase and rapeseed oil were demonstrated to support optimal iturin A production. And simultaneous hydrolysis with lipase and fermentation was an effective way to produce iturin A from RSC using B. amyloliquefaciens CX-20.

Highlights

Rapeseed cake (RSC), as the intermediate by-product of oil extraction from the seeds of Brassica napus, can be converted into rapeseed meal (RSM) by solvent extraction to remove oil
20 g/L initial glucose was used to test the influence of initial RSC concentration on iturin A production by B. amyloliquefaciens CX-20
The iturin A production started to decrease upon further increase of RSC concentration from 90 to 150 g/L

Summary

Introduction

Rapeseed cake (RSC), as the intermediate by-product of oil extraction from the seeds of Brassica napus, can be converted into rapeseed meal (RSM) by solvent extraction to remove oil. Rapeseed cake (RSC) and RSM are the major byproducts in the production of rapeseed oil and are mainly composed of proteins, carbohydrates and minerals. Both are good protein resources for animal feed, with a favorable balance of essential and sulfur-containing amino acids [9]. The reasons are as follows: (1) the production technology of RSC is more environmentally friendly [11], (2) RSC has a higher metabolizable energy value due to its higher residual oil content [12], and (3) organic animal production precludes the use of oilseed meal due to the exposure to chemical solvents during the extraction [13]. If the problem of high oil content in RSC can be solved, it is likely that RSC can be used for microbial production to RSM

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