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Journal of Zhejiang University SCIENCE B
ISSN 1673-1581(Print), 1862-1783(Online), Monthly
2016 Vol.17 No.4 P.262-270
Changes in the physiological properties and kinetics of citric acid accumulation via carbon ion irradiation mutagenesis of Aspergillus niger
Abstract: The objective of this work was to produce citric acid from corn starch using a newly isolated mutant of Aspergillus , and to analyze the relationship between changes in the physiological properties of A. induced by carbon ion irradiation and citric acid accumulation. Our results showed that the physiological characteristics of conidia in A. niger were closely related to citric acid accumulation and that lower growth rate and viability of conidia may be beneficial to citric acid accumulation. Using corn starch as a raw material, a high-yielding citric acid mutant, named HW2, was obtained. In a 10-L bioreactor, HW2 can accumulate 118.9 g/L citric acid with a residual total sugar concentration of only 14.4 g/L. This represented an 18% increase in citric acid accumulation and a 12.5% decrease in sugar utilization compared with the original strain.
Key words: Carbon ion irradiation, Physiological properties, Mutation, Citric acid accumulation
创新点：首次报道了碳离子束对黑曲霉生理特性的影响，提出黑曲霉生理特性的改变对其柠檬酸的积累有影响。
方法：（1）孢子直径和孢子活力的测定：利用流式细胞仪对两株黑曲霉突变菌株以及原始菌株进行了孢子直径测定。通过该实验说明碳离子束可以诱导黑曲霉孢子直径发生改变（表1）。利用MTT法，测定了突变菌株和原始菌株孢子活力。同时，通过该实验表明碳离子束可以诱导黑曲霉孢子活力发生改变（图1）。（2）生长速率的测定：利用不同糖分的平板生长法测定了突变体和原始菌株生长速度的差异。通过该实验说明碳离子束可以诱导黑曲霉生长速率发生改变（图3和图4）。（3）柠檬酸积累实验：利用摇瓶发酵实验和10 L发酵罐扩培实验测定了突变体和原始菌株柠檬酸积累的差异。通过该实验说明生理特性改变的突变体与原始菌株在柠檬酸积累上存在显著差异（图6~8）。
结论：通过两株黑曲霉突变体与原始菌株之间生理特性的差异研究，我们发现黑曲霉生理特性的改变对其柠檬酸积累有一定的影响，低的黑曲霉孢子活力以及生长速率对柠檬酸的积累是有益的。最终，获得了一株高产菌株HW2，其10 L发酵罐柠檬酸的积累能力比原始菌株提高了18%。
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DOI:
10.1631/jzus.B1500120
CLC number:
Q819
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On-line Access:
2016-04-05
Received:
2015-05-16
Revision Accepted:
2015-12-08
Crosschecked:
2016-03-15