Industrial robustness linked to the gluconolactonase from Zymomonas mobilis.
The physiological characteristics and the potential gluconolactone production of the gluconolactonase-deficient strain, Zymomonas mobilis ZM4 gnlΔ, were investigated via growth inhibitory assay and biotransformation of glucose and fructose into gluconolactone and sorbitol, respectively. The results of ethanol fermentation studies performed in the presence of high concentration of glucose (>200 g l-1) under fermentative or aerobic conditions indicated that a significant reduction of volumetric ethanol productivity from the strain of ZM4 gnlΔ was noticeable due to the reduced rates of specific growth, sugar uptake, and biomass yield as compared with those of the parental strain ZM4. The biotransformation prepared at pH 6.0 using the permeabilized cell indicated that gluconic acid from ZM4 gnlΔ was still produced as a major product (67 g l-1) together with sorbitol (65 g l-1) rather than gluconolactone after 24 h. Only small amount of gluconolactone was transiently overproduced up to 9 g l-1, but at the end of biotransformation, all gluconolactone were oxidized into gluconic acid. This indicated that autolysis of gluconolactone at the pH led to such results despite under gluconolactonase inactivation conditions. The physiological characteristics of ZM4 gnlΔ was further investigated under various stress conditions, including suboptimal pH (3.5~6.0), temperature (25~40 °C), and presence of growth inhibitory molecules including hydrogen peroxide, ethanol, acetic acid, furfural, and so forth. The results indicated that ZM4 gnlΔ was more susceptible at high glucose concentration, low pH of 3.5, and high temperature of 40 °C and in the presence of 4 mM H2O2comparing with ZM4. Therefore, the results were evident that gluconolactonase in Z. mobilis contributed to industrial robustness and anti-stress regulation.
School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Kensington, 2052, Australia.
Alfonsus
A
Alvin
Department of Microbiology, Pukyong National University, Busan, 608-737, Republic of Korea.
Junhyun
J
Kim
Department of Biotechnology, Pukyong National University, Busan, 608-737, Republic of Korea.
Gwi-Taek
GT
Jeong
Department of Science and Environmental Studies, The Education University of Hong Kong, Tai Po, New Territories, Hong Kong.
Yiu Fai
YF
Tsang
Department of Environment and Energy, Sejong University, Seoul, 143-747, Republic of Korea.
Eilhann E
EE
Kwon
School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Kensington, 2052, Australia.|School of Environmental and Life Science, The University of Newcastle, Newcastle, Australia.
Brett A
BA
Neilan
School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Kensington, 2052, Australia. youngjaejeon@pknu.ac.kr.|Department of Microbiology, Pukyong National University, Busan, 608-737, Republic of Korea. youngjaejeon@pknu.ac.kr.
Young Jae
http://orcid.org/0000-0002-4867-9812
YJ
Jeon
D018533:Biomass; D001711:Biotransformation; D002265:Carboxylic Ester Hydrolases / Q000235:genetics* / Q000378:metabolism*; D000431:Ethanol / Q000378:metabolism; D005285:Fermentation; D005632:Fructose / Q000378:metabolism; D055786:Gene Knockout Techniques; D005942:Gluconates / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D007218:Industrial Microbiology; D007783:Lactones / Q000378:metabolism*; D013012:Sorbitol / Q000378:metabolism; D013312:Stress, Physiological; D017355:Zymomonas / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development / Q000502:physiology*
D005942:Gluconates; D007783:Lactones; D005632:Fructose; D000431:Ethanol; D013012:Sorbitol; D006861:Hydrogen Peroxide; D002265:Carboxylic Ester Hydrolases; C020579:gluconolactonase; D005947:Glucose; C010730:beta-glucono-1,5-lactone
Gene knockout; Gluconolactonase-deficient strain; Gluconolactone; Robustness; Stress response; Zymomonas mobilis