Mutation-Screening in Xylanase-Producing Strains by Ion Implantation

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Low energy ion beam has been widely applied in microbe breeding, plant breeding, gene transfer and cell modification. In this study, the Escherichia coli (E.coli) strain producing tryptophanase was irradiated by a low energy nitrogen ion beam with an energy of 10 keV at a fluence of 13 × 10 14 N + /cm 2 when glycerin at a 15% concentration was used as a protector. The effect on the biomass of E. coli after N + implantation was analyzed in detail by statistic methods. The screening methods used in this study were proven to be effective. After continuous mutagenicity, a high-yield tryptophanase strain was selected and both its biomass and enzymatic activity were higher than those of the parent strain. The results of scale-up production showed that the biomass could reach wet weight 8.2 g/L and 110 g L-tryptophan could be formed in the volume of the 1 l enzymatic reaction system.

Section: Determination Of N + Implantation Parameterssupporting

confidence: 80%

A Study of Mutation Breeding of High-Yielding Tryptophanase Escherichia coli by Low-Energy N⁺Ion Beam Implantation

Min

Yang

Wang³

2009

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“…The results showed that the optimum implanting ion species is N + . It has been well proven that N + has a higher mutation rate and a wider mutation spectrum than other ion species [19] . By means of N + implantation the mutant strain AF-ANm16, that does not produce red pigment in the fermentation process, was obtained.…”

Section: Discussionmentioning

confidence: 99%

The Breeding of a Pigment Mutant Strain of Steroid Hydroxylation Aspergillus Flavus by Low Energy Ion Implantation

Feng

et al. 2009

In the process of the fermentation of steroid C11α-hydroxylgenation strain Aspergillus flavus AF-ANo208, a red pigment is derived, which will affect the isolation and purification of the target product. Low energy ion beam implantation is a new tool for breeding excellent mutant strains. In this study, the ion beam implantation experiments were performed by infusing two different ions: argon ion (Ar + ) and nitrogen ion (N + ). The results showed that the optimal ion implantation was N + with an optimum dose of 2.08×10 15 ions/cm 2 , with which the mutant strain AF-ANm16 that produced no red pigment was obtained. The strain had high genetic stability and kept the strong capacity of C11α-hydroxylgenation, which could be utilized in industrial fermentation. The differences between the original strain and the mutant strain at a molecular level were analyzed by randomly amplified polymorphic DNA (RAPD). The results indicated that the frequency of variation was 7.00%, which would establish the basis of application investigation into the breeding of pigment mutant strains by low energy ion implantation.

“…Reducing sugars and xylanase activity were determined with 3,5 dinitrosalicylic acid [13] . The enzymatic activities of the samples were determined after centrifuging the cultures for 20 min at 1000 g at the room temperature.…”

Section: Assay Of Xylanase Activitymentioning

confidence: 99%

“…In order to obtain the highest positive mutation and survival rate, 10 keV was chosen as the optimum energy based on the theory in Ref. [13] The survival rate was also related to the dose of N + implantation. A characteristic curve is shown in Fig.…”

Section: Determination Of N + Implantation Parametermentioning

confidence: 99%

Studies on Mutation Breeding of High-Yielding Xylanase Strains by Low-Energy Ion Beam Implantation

Yang

Zhengling

2007

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As a new mutagenetic method low-energy ion implantation has been used widely in many research areas in recent years. In order to obtain some industrial strains with high xylanase yield, the wild type strain Aspergillus niger A3 was mutated by means of nitrogen ions implantation (10 keV, 2.6× 10 14 ∼ 1.56 × 10 15 ions/cm 2 ) and a mutant N212 was isolated subsequently. However, it was found that the initial screening means of the high-yielding xylanase strains such as transparent halos was unfit for first screening. Compared with that of the wild type strain, xylanase production of the mutant N212 was increased from 320 IU/ml to 610 IU/ml, and the optimum fermentation temperature was increased from 28 o C to 30 o C.