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Industrial robustness linked to the gluconolactonase from Zymomonas mobilis

Alvin, Alfonsus,Kim, Junhyun,Jeong, Gwi-Taek,Tsang, Yiu Fai,Kwon, Eilhann E.,Neilan, Brett A.,Jeon, Young Jae Springer-Verlag 2017 Applied Microbiology and Biotechnology Vol.101 No.12
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<P>The physiological characteristics and the potential gluconolactone production of the gluconolactonase-deficient strain, Zymomonas mobilis ZM4 gnl Delta, 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 gnl Delta 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 gnl Delta 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 gnl Delta was further investigated under various stress conditions, including suboptimal pH (3.5 +/- 6.0), temperature (25 +/- 40 A degrees C), and presence of growth inhibitory molecules including hydrogen peroxide, ethanol, acetic acid, furfural, and so forth. The results indicated that ZM4 gnl Delta was more susceptible at high glucose concentration, low pH of 3.5, and high temperature of 40 A degrees C and in the presence of 4 mM H2O2 comparing with ZM4. Therefore, the results were evident that gluconolactonase in Z. mobilis contributed to industrial robustness and anti-stress regulation.</P>
2
Molecular Classification of Commercial Spirulina Strains and Identification of Their Sulfolipid Biosynthesis Genes

( Kwei Chee Kuan ),( David Lewis ),( Keith King ),( William Donohue ),( Brett A. Neilan ) 한국미생물 · 생명공학회 2011 Journal of microbiology and biotechnology Vol.21 No.4
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Cyanobacterial strains of the genus Spirulina have recently been identified as an excellent source of sulfolipids, some of which possess anti-HIV properties. Thus, to investigate the distribution of sufolipid biosynthesis pathways in Spirulina, a genetic screening/phylogentic study was performed. Five different strains of Spirulina [Spirulina (Jiangmen), Spirulina sp., S. platensis, S. maxima, and Spirulina seawater] sourced from different locations wereinitially classified via 16S rDNA sequencing, and then screened for the presence of the sulfolipid biosynthesis genes sqdB and sqdX via a PCR. To assess the suitability of these strains for human consumption and safe therapeutic use, the strains were also screened for the presence of genes encoding nonribosomal peptide synthases (NRPSs) and polyketide synthases (PKSs), which are often associated with toxin pathways in cyanobacteria. The results of the 16S rDNA analysis and phylogenetic study indicated that Spirulina sp. is closely related to Halospirulina, whereas the other four Spirulina strains are closely related to Arthrospira. Homologs of sqdB and sqdX were identified in Spirulina (Jiangmen), Spirulina sp., S. platensis, and the Spirulina seawater. None of the Spirulina strains screened in this study tested positive for NRPS or PKS genes, suggesting that these strains do not produce NRP or PK toxins.