Production of the secondary metabolites γ-aminobutyric acid and monacolin K by <Emphasis Type="Italic">Monascus</Emphasis>

γ-Aminobutyric acid (GABA), a hypotensive agent, and monacolin K, a cholesterol-lowering drug, can be produced by Monascus spp. Under optimal culture conditions, the products of fermentation using Monascus spp. may serve as a multi-functional dietary supplement and can prevent heart disease. In this study, Monascus purpureus CCRC 31615, the strain with the highest amount of monacolin K, was identified from 16 strains using solid fermentation. Its GABA productivity was particularly high. Addition of sodium nitrate during solid-state fermentation of M. purpureus CCRC 31615 improved the productivity of monacolin K and GABA to 378 mg/kg and 1,267.6 mg/kg, respectively. GABA productivity increased further to 1,493.6 mg/kg when dipotassium hydrophosphate was added to the medium. Electronic Publication     

Oviposition by autumn gum moth (Mnesampela privata) in relation to Eucalyptus globulus defoliation, larval performance and natural enemies

Abstract 1 Eucalyptus globulus Labill. exhibited consistent intraspecific variation in oviposition choice by Mnesampela privata (Guenée) (Lepidoptera: Geometridae) in field surveys of host plants that had been designated, based on the prior season's defoliation levels, as resistant or susceptible to M. privata. At both field sites significantly fewer egg batches were found on resistant compared to susceptible trees. 2 In cage bioassays we demonstrated a significant oviposition preference by M. privata, with over two‐fold greater number of egg batches laid on foliage sprigs from susceptible compared to resistant trees. Despite differences in tree oviposition choice, we found no evidence in the field or the laboratory of adult females adjusting egg batch size in accordance to oviposition preference. 3 Caged larval survival, development times and pupal weight did not vary significantly between resistant and susceptible trees. Similarly, in a laboratory feeding experiment, neonates utilized resistant and susceptible foliage equally. 4 Larval mortality in the field attributed to natural enemies did not vary significantly between resistant and susceptible trees, nor did the percentage of Telenomus sp. parasitism of M. privata eggs within a batch and batches per tree. 5 Failure to associate either larval performance or natural enemy efficacy with the observed intraspecific variation in E. globulus susceptibility to M. privata oviposition indicates that some other unidentified factors drive the evolution of host selection for oviposition.     

Isolation and characterization of a bacterium that mineralizes toluene in the absence of molecular oxygen

A bacterium tentatively identified as a Pseudomonas sp. was isolated from a laboratory aquifer column in which toluene was degraded under denitrifying conditions. The organism mineralized toluene in pure culture in the absence of molecular oxygen. In carbon balance studies using [ring-UL-¹⁴C]toluene, more than 50% of the radioactivity was recovered as ¹⁴CO₂. Nitrate and nitrous oxide served as electron acceptors for toluene mineralization. The organism was also able to degrade m-xylene, benzoate, benzaldehyde, p-cresol, p-hydroxybenzaldehyde, p-hydroxybenzoate and cyclohexanecarboxylic acid in the absence of molecular oxygen.     

Structural Analysis of an Extracellular Polysaccharide of Porodisculus pendulus

The aroL gene, encoding shikimate kinase of Brevibacterium lactofermentum, a coryneform glutamic acid-producing bacterium, was cloned. Recombinant plasmids containing the aroL gene caused elevated levels of shikimate kinase synthesis in B. lactofermentum. It was found that in addition to the aroL gene, the aroB and aroE genes, encoding dehydroquinate synthase and shikimate dehydrogenase, respectively, also existed on these recombinant plasmids, in complementation tests with various Escherichia coli and B. lactofermentum aromatic amino acid auxotrophs. The aroL, aroB and aroE genes of B. lactofermentum are located closely on the cloned DNA fragment, in that order. It was shown that at least these three aro genes form a cluster on the chromosome of B. lactofermentum.     

Catalytic properties of β-cyclodextrin glucanotransferase from alkalophilic<Emphasis Type="Italic">Bacillus</Emphasis> sp. BL-12 and intermolecular transglycosylation of stevioside

The catalytic properties of β-cyclodextrin glucanotransferase (β-CGTase) from alkalophilicBacillus sp. BL-12 specific for the intermolecular transglycosylation of stevioside were investigated. The molecular mass of purified β-CGTase by ultra-filtration and β-cyclodextrin polymer affinity chromatography was estimated to be 90 kDa, which is high compared to other known bacterial CGTases. The optimal pH and temperature were 9.0 and 50°C, respectively, and thermal stability at 40°C was elevated 10-fold in the presence of 1% maltodextrin. The kinetic parameters of the new β-CGTase from alkalophilicBacillus sp. BL-12 indicate that it is more suitable for transglycosylation than the cyclization reaction. Maltodextrin was the most suitable glycosyl donor for transglycosylation of stevioside. The transglycosylation of stevioside was carried out using 60 units of CGTase per gram of maltodextrin, 20 g/L stevioside as the glycosyl acceptor, and 50 g/L maltodextrin as the gycosyl donor at 40°C for 6 h, and a conversion yield of stevioside as high as 76% was obtained.     

Isolation and characterization of Halomonas sp. strain IMPC, a p-coumaric acid-metabolizing bacterium that decarboxylates other cinnamic acids under hypersaline conditions

A moderately halophilic, mesophilic, Gram-negative, motile, nonsporulating bacterium, designated strain IMPC, was isolated from a table-olive fermentation rich in aromatic compounds, after enrichment on p-coumaric acid under halophilic conditions. Strain IMPC was able to degrade p-coumaric acid. p-hydroxybenzaldehyde and p-hydroxybenzoic acid were detected as breakdown products from p-coumaric acid. Protocatechuic acid was identified as the final aromatic product of p-coumaric acid catabolism before ring fission. Strain IMPC transformed various cinnamic acids with substituent H, OH, CH(3) or OCH(3) in the para- and/or meta-position of the aromatic ring to the corresponding benzoic acids, indicating a specific selection. A beta-oxidation pathway was proposed for these transformations. Phylogenetic analysis of the 16S rRNA gene revealed that this isolate was a member of the genus Halomonas. Strain IMPC was closely related to Halomonas elongata ATCC 33173(T)and Halomonas eurihalina ATCC 49336(T).     

Characterization of an α-haloalkanoic acid–degrading Pseudomonas aeruginosa MX1 isolated from contaminated seawater

Halogenated compounds such as α-halocarboxylix acids (αHAs) are widely liberated into the ecosystem through the prevailing xenobiotic activities that involve the use of herbicides for weed management in the agricultural sector and mass production of various commercial halogenated chemical intermediates. Since such compounds exert stress on the environment owing to their recalcitrance and are not easily degraded, the study aimed to isolate, identify, and characterize dehalogenase-producing bacteria with the purpose of bioremediation. The MX1 bacterium was successfully isolated from seawater samples off the coast of Desaru, Malaysia, using an enrichment technique supplemented with 2,2-dichloropropionic acid (2,2-DCP). Interestingly, the MX1 strain grew best in a 20 mM 2,2-DCP minimal medium as the sole carbon source and illustrated a 44 ± 0.2 h cell-doubling time as well as a 38 μmol Cl^?/ml maximum rate of chloride ion release. However, 2,2-DCP–containing medium with concentrations that exceeded 30 mM inhibited the growth of the MX1, possibly attributable to the increased toxicity of the compound on the bacteria. Biochemical examinations and 16S rDNA sequence analysis revealed that the MX1 strain shares high identity to Pseudomonas aeruginosa, and the gene sequence was deposited into GenBank as Pseudomonas aeruginosa MX1 under accession number KP336490. The presence of the putative dehalogenase gene in the MX1 strain was established by polymerase chain reaction (PCR) analysis, which proved the presence of conserved amino acid residues belonging to the Group I dehalogenase. This is the first report detailing a P. aeruginosa strain capable of degrading the recalcitrant 2,2-DCP and its functional amino acid residues.     

Regulation of CO on heterocyst differentiation and nitrate uptake in the cyanobacterium Anabaena sp. PCC 7120

AIMS: The aim of the present investigation was to study the effects of different inorganic carbon and nitrogen sources on nitrate uptake and heterocyst differentiation in the culture of cyanobacterium Anabaena sp. PCC 7120. METHODS AND RESULTS: Anabaena was cultivated in media BG11 containing combined nitrogen and supplementary NaHCO3 or CO2. Cell growth, heterocyst differentiation, nitrate reductase (NR, EC 1.7.7.2), glucose-6-phosphate dehydrogenase (G6PDH, EC 1.1.1.49) and NO uptake were analysed. The cells cultivated in BG11(0) medium with aeration were taken as reference. Experimental results showed that the differentiation frequency of heterocysts when the cells were cultivated with elevated CO2 was higher than that of the cells grown with air or bicarbonate. Heterocysts appeared unexpectedly when CO2 was introduced into the medium containing nitrate. However, no heterocysts emerged when CO2 was added to medium containing NH or urea, or when NaHCO3 was supplied to the medium with nitrate. Both nitrate uptake rate and nitrate reduction enzyme activity were depressed by the supplement of CO2 to the culture. The activity of G6PDH was enhanced with the increase in heterocyst differentiation frequency. CONCLUSION: CO2 might compete with NO for energy and electrons in the uptake process and CO2 appears favoured. This led to a high intracellular C/N ratio and a relative N limitation. So the process of heterocyst differentiation was activated to supplement nitrogen uptake. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provided an attractive possibility to form more heterocysts by rapid growth of Anabaena cells cultivated in the medium containing nitrate in order to increase nitrogen fixation and hydrogen production.