Characterization of optimal growth conditions and carotenoid production of strain Rhodotorula mucilaginosa HP isolated from larvae of Pieris rapae

Yeasts have been studied because of their production of a pigment known as carotenoid with potential application in food and feed supplements. A carotenoid‐producing yeast was isolated from the larvae of Pieris rapae, named HP. The strain HP was identified as Rhodotorula mucilaginosa classified by its carbohydrate fermentation pattern and physiological tests. Rhodotorula mucilaginosa HP produces several exogenous enzymes: alkaline phosphatase, esterase, leucine arylamidase, valine arylamidase, acid phosphatase and β‐glucosidase. Using response surface methodology, selected medium components (yeast extract, malt extract, peptone, glucose) were tested to find the optimum conditions for carotenoid production and the growth of R. mucilaginosa HP. Central composite design was used to control the concentrations of medium components. Peptone and glucose had the largest effects on carotenoid production and cell growth of R. mucilaginosa HP, respectively. The estimated optimal growth conditions of R. mucilaginosa HP were: yeast extract 3.23%, malt extract 2.84%, peptone 6.99% and glucose 12.86%. The estimated optimal conditions for carotenoid production were: yeast extract 2.17%, malt extract 2.11%, peptone 5.79% and glucose 12.46%. These results will assist in the formulation of an appropriate culture medium for optimal carotenoid production of R. mucilaginosa HP for commercial use.     

A comparative analysis of microflora during biofilm development on grape seeds exposed to methanol in a biofilter

The attachment of microorganisms onto biotic surfaces to form biofilm structures on the support media of a biofilter has great impact on biodegradation systems. This study examined the composition of the microbial community that developed on grape seeds (GS) used as support media in methanol degradation biofilters. They were analyzed using conventional microbiology techniques and API galleries. Analysis of microbial counts showed that, in GS before methanol exposure, bacteria and filamentous fungi were predominant over yeasts. In contrast, GS exposed to methanol exhibited more bacteria and yeasts than fungi. Most of the Gram-negative bacteria were the Pseudomonas genus, Bacillus staerothermophilus, Bacillus amyloliquefaciens, and Bacillus pumilus. Rhodotorula mucilaginosa was the primary yeast found. The filamentous fungi Aspergillus sp. Cladosporium cladosporioides, Fusarium sp., and Alternaria sp. were also detected. No Gram-positive bacteria growth was found on GS exposed to methanol. Using scanning electron microscopy, biofilm formation on the GS was examined to reveal the presence of both prokaryotic and eukaryotic microorganisms as biomass accumulation was visible on the seeds. Seeds exposed to methanol for 90 days showed a mature biofilm with cuticle and epidermal layer decline, as well as biofilm dissolution into grape seed integuments.     

Biomass and carotenoid pigment production by patagonian native yeasts

Summary New yeast isolates from unexplored Patagonian habitats were studied for the production of biomass and carotenoids as the first step towards the selection of hyper-producing strains and the design of a process optimization approach. Patagonian yeast isolates considered as potential biomass and carotenoid sources were studied using ammonium sulphate and urea as nitrogen sources in semi-synthetic medium (MMS), and agro-industrial byproducts (cane molasses, corn syrup, raw malt extract) as carbon sources. Maximum pigment production (300 μg g⁻¹) was achieved by Rhodotorula mucilaginosa CRUB 0195 and by novel species Cryptococcus sp. CRUB 1046. β-carotene, torulene and torularhodin were the major carotenoids found.     

Bioprospecting microbes for single-cell oil production from starchy wastes

Production of lipid from oleaginous yeast using starch as a carbon source is not a common practice; therefore, the purpose of this investigation was to explore the capability of starch assimilating microbes to produce oil, which was determined in terms of biomass weight, productivity, and lipid yield. Saccharomyces pastorianus, Rhodotorula mucilaginosa, Rhodotorula glutinis, and fungal isolate Ganoderma wiiroense were screened for the key parameters. The optimization was also performed by one-factor-at-a-time approach. Considering the specific yield of lipid and cell dry weight yield, R. glutinis and R. mucilaginosa showed superiority over other strains. G. wiiroense, a new isolate, would also be a promising strain for starch waste utilization in terms of extracellular and intracellular specific yield of lipids. Extracellular specific yield of lipid was highest in R. glutinis culture (0.025?g?g^?1 of biomass) followed by R. mucilaginosa (0.022?g?g^?1 of biomass) and G. wiiroense (0.020?g?g^?1 of biomass). Intracellular lipid was again highest in R. glutinis (0.048?g?g^?1 of biomass). The most prominent fatty acid methyl esters among the lipid as detected by GC-MS were saturated lipids mainly octadecanoic acid, tetradecanoate, and hexadecanoate. Extracellular lipid produced on starch substrate waste would be a cost-effective alternative for energy-intensive extraction process in biodiesel industry.     

The Composition of Jerusalem Artichoke (Helianthus tuberosus L.) Spirits Obtained from Fermentation with Bacteria and Yeasts

The composition of spirits distilled from fermentation of Jerusalem artichoke (Helianthus tuberosus L.) tubers was compared by means of gas chromatography. The microorganisms used in the fermentation processes were the bacterium Zymomonas mobilis, strains 3881 and 3883, the distillery yeast Saccharomyces cerevisiae, strains Bc16a and D₂ and the Kluyveromyces fragilis yeast with an active inulinase. The fermentation of mashed tubers was conducted using a single culture of the distillery yeast Saccharomyces cerevisiae and the bacterium Zymomonas mobilis (after acid or enzymatic hydrolysis) as well as Kluyveromyces fragilis (sterilized mashed tubers). The tubers were simultaneously fermented by mixed cultures of the bacterium or the distillery yeast with K. fragilis. The highest ethanol yield was achieved when Z. mobilis 3881 with a yeast demonstrating inulinase activity was applied. The yield reached 94 % of the theoretical value. It was found that the distillates resulting from the fermentation of mixed cultures were characterized by a relatively lower amount of by‐products compared to the distillates resulting from the single species process. Ester production of 0.30–2.93 g/L, responsible for the aromatic quality of the spirits, was noticed when K. fragilis was applied for ethanol fermentation both in a single culture process and also in the mixed fermentation with the bacterium. Yeast applied in this study caused the formation of higher alcohols to concentrations of 7.04 g/L much greater than those obtained with the bacterium. The concentrations of compounds other than ethanol obtained from Jerusalem artichoke mashed tubers, which were fermented by Z. mobilis, were lower than those achieved for yeasts.     

Intracellular Biosynthesis and Removal of Copper Nanoparticles by Dead Biomass of Yeast Isolated from the Wastewater of a Mine in the Brazilian Amazonia

In this study was developed a natural process using a biological system for the biosynthesis of nanoparticles (NPs) and possible removal of copper from wastewater by dead biomass of the yeast Rhodotorula mucilaginosa. Dead and live biomass of Rhodotorula mucilaginosa was used to analyze the equilibrium and kinetics of copper biosorption by the yeast in function of the initial metal concentration, contact time, pH, temperature, agitation and inoculum volume. Dead biomass exhibited the highest biosorption capacity of copper, 26.2 mg g⁻¹, which was achieved within 60 min of contact, at pH 5.0, temperature of 30°C, and agitation speed of 150 rpm. The equilibrium data were best described by the Langmuir isotherm and Kinetic analysis indicated a pseudo-second-order model. The average size, morphology and location of NPs biosynthesized by the yeast were determined by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM). The shape of the intracellularly synthesized NPs was mainly spherical, with an average size of 10.5 nm. The X-ray photoelectron spectroscopy (XPS) analysis of the copper NPs confirmed the formation of metallic copper. The dead biomass of Rhodotorula mucilaginosa may be considered an efficiently bioprocess, being fast and low-cost to production of copper nanoparticles and also a probably nano-adsorbent of this metal ion in wastewater in bioremediation process.     

Distribution of Marine Red Yeasts in Shrimps and the Environments of Shrimp Culture

Populations of marine red yeast from shrimps and the environments of shrimp culture were investigated from various areas at Zhanjiang in China. All strains were studied for the production of biomass and carotenoids. We isolated 88 marine red yeast strains and the average populations of marine red yeast in seawater and the water from shrimp culture ponds were 70.0 and 172.4 CFU per 100 ml water, respectively. For shrimp samples, average populations of marine red yeast from gills, intestines, and stomachs were 178.0, 15.0, and 8.0 CFU per shrimp, respectively. The isolates were grouped into nine species belonging to three genera as follows: Rhodosporidium, Rhodotorula, and Sporidiobolus. R. sphaerocarpum had the highest average biomass yield (10.3 ± 0.88 g/l), followed by S. ruineniae (10.1 g/l) and Rh. mucilaginosa (9.9 ± 1.75 g/l). R. paludigenum had the highest average carotenoid yield (2.83 ± 0.589 mg/l), followed by S. pararoseus (2.72 mg/l) and R. sphaerocarpum (2.59 ± 0.454 mg/l). The results showed that marine red yeasts were normal microbial components in the environments of shrimp culture and shrimps, and carotenoids are abundant in these marine red yeast.     

Biodegradation of sodium sulfite liquor (NaSSL) and sodium lignosulfonate (NaLS) by a mixed culture of microorganisms

Summary In this work we discuss the aerobic biodegradation of sodium sulfite liquor of (NaSSL) and sodium lignosulfonate (NaLS) in a firwood sulfite waste liquor by a mixed culture of microorganisms consisting of two Trichosporon yeasts and bacteria in the Arthrobacter (two species), Pseudomonas and Chromabacterium genera. Under established process parameters, the NaSSL was biodegradated in one or two stages by mixed cultures. The kinetics in each stage was studied. The optimal ratio of NaLS and sugars in the substrate for the growth of mixed culture was determined. The growth of the monocultures of the bacteria on the NaLS and the growth of the yeasts as monocultures on the NaSSL substrate were examined. UV absorption and IR spectra were employed as analytical methods to follow the microbial degradation of NaLS. The aim of this research was to study the biodegradation process and kinetics and to remove by means of mixed culture the maximum amount of organic matter from NaSSL.     

Anaerobic degradation of chlorophenol by an enrichment culture

Summary An anaerobic mixed culture from sewage sludge was enriched in a yeast extract and peptone-containing medium; it was able to degrade 2-cholorophenol completely to methane and CO₂. Degradation rates of 2-chlorophenol of up to 0.18 g/l per day were observed in suspended cultures without biomass retention and of 0.375 g/l per day in cultures immobilized on Liapor clay beads. Attempts to isolate the dechlorinating organism failed. The mixed culture was reduced to three morphologically distinctive microorganisms using a medium with limited amounts of yeast extract and peptone and n-butyrate as a co-substrate. Under these conditions the phenol-degrading bacterium was lost and phenol accumulated in the medium. No growth and no dehalogenation of 2-chlorophenol was obtained when yeast extract and peptone were omitted completely. Besides serving as a source of supplementary components, yeast extract and peptone were apparently required as the main source of carbon, wereas reducing equivalents for reductive dehalogenation were obtained by oxidation of n-butyrate. A spirochaete-like organism was presumably the dechlorinating bacterium. The mixed culture lost its dehalogenation capability if this organism was lost. n-Butyrate could be replaced by n-valerate, hexanoate, heptanoate, octanoate, pelargonic acid, n-decanoic acid or palmitate as co-substrates for dehalogenation of either 2-chlorophenol, 2-bromophenol or complete dechlorination of 2,6-dichlorophenol, whereas from 2,4-dichlorophenol only the substituent in the ortho-position could be eliminated.Dedicated to Professor O. Kandler on the occassion of his 70th birthdayOffprint requests to: J. Winter     

Use of exogenous specialised bacteria in the biological detoxification of a dump site‐polychlorobiphenyl‐contaminated soil in slurry phase conditions

The possibility of biologically detoxifying a contaminated soil from an Italian dump site containing about 1500 mg/kg (in dry soil) of polychlorinated biphenyls was studied in the laboratory in this work. The soil, which contained indigenous aerobic bacteria capable of growing on biphenyl or on monochlorobenzoic acids at concentration of about 300 CFU per g of air‐dried soil, was amended with inorganic nutrients, saturated with water and treated in aerobic 3‐L batch slurry reactors (soil suspension at 20% w/v). Either Pseudomonas sp. CPE1 strain, capable of cometabolising low‐chlorinated biphenyls into chlorobenzoic acids, or a bacterial co‐culture capable of aerobically dechlorinating polychlorobiphenyls constituted by this bacterium and the two chlorobenzoic acid degrading bacteria Pseudomonas sp. CPE2 strain and Alcaligenes sp. CPE3 strain, were used as inocula (final concentration of about 10⁸ CFU/mL for each bacterium), in the absence and in the presence of biphenyl (4 g/kg of air dried soil). Significant soil polychlorobiphenyl depletions were observed in all the reactors after 119 days of treatment. The soil inoculation with the sole CPE1 was found to slightly enhance the polychlorobiphenyl depletions (about 20%) and the soil detoxification; the effect was higher in the presence of biphenyl. The use of the polychlorobiphenyl mineralising bacterial co‐culture as inoculum resulted in a strong enhancement of the depletions of both the soil polychlorobiphenyls (from 50 to 65%) and of the original soil ecotoxicity. The bacterial biomass inoculated was found to implant into the soil; the higher specialised biomass availability thus reached in the inoculated soil was probably responsible of a more extensive biodegradation of polychlorobiphenyls and therefore of the higher detoxification yields observed in the inoculated reactors. The soil ecotoxicity, measured through two different soil contact assays, i.e., the Lepidium sativum germination test and the Collembola mortality test, was often found to decrease proportionally with the soil polychlorobiphenyl concentration. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 64: 240–249, 1999.     

Studies on Production of Biotin by Microorganisms

The utilization of hydrocarbons by microorganisms was studied in many fields, but the production of biotin vitamers by hydrocarbon-utilizing bacteria has never been reported.

We have screened many hydrocarbon-utilizing bacteria which produce biotin vitamers in the culture broth. The effects of cultural conditions on biotin vitamers production by strain 5–2, tentatively assigned to the genus Pseudomonas, were studied.

More than 98% of biotin vitamers produced from hydrocarbons by strain 5–2 was chromatographically determined as desthiobiotin. As nitrogen source, natural nutrients were more effective than inorganic nitrogen sources. The production of biotin vitamers was increased under the condition of good aeration. Exogenous pimelic or azelaic acid enhanced biotin vitamers production by strain 5–2.

The production of biotin vitamers from n-alkanes, n-alkenes or glucose by an isolated bacterium, strain 5-2, tentatively assigned to the genus Pseudomonas, was investigated. Among these carbon sources, n-undecane was the most excellent for biotin vitamers production.

The biosynthetic pathway of biotin vitamers, especially desthiobiotin, from n-undecane was also studied. It was found by thin-layer and gas-liquid chromatographical methods that pimelic and azelaic acids were the main acid components in n-undecane culture.

This result, together with previously reported enhancement of biotin vitamers production by these acids, suggests that pimelic and azelaic acids may be the intermediates of biotin vitamers biosynthesis from n-undecane.     

Growth of Thermus aquaticus and its TaqI endonuclease production

The culture behaviour of Thermus aquaticus was characterized. The response of the bacterium to various carbon (tryptone, glucose, glycerol) and nitrogen sources (yeast extract, NaNO₃, (NH₄)₂SO₄, leucine, thymine, thiamine, glutamic acid) was studied. Amino acids did not support growth, but CASTENHOLZ salt medium supplemented with yeast extract and glucose or tryptone resulted in good growth and production. A suitable medium composition giving the highest biomass concentration and enzyme yield was developed. The simple medium containing TYE-NaCl resulted in the highest biomass concentration, whereas CASTENHOLZ mineral medium supplemented with tryptone and yeast extract gave the highest specific activity and enzyme yield. The effect of inoculum age and size on growth was also investigated in order to improve the yield and process consistency. The use of shake flasks inoculated with precultures at their early or late stationary phase resulted in the same biomass concentration (0.56 ± 0.015 g/l) and similar maximum specific growth rates (0.258 ± 0.003 h^?1). Inoculum sizes between 1 and 2.5 per cent were optimal for cell growth. As the other papers on thermophilic microorganisms, including the T. aquaticus YT-1 strain, gave qualitative information on growth, the results presented here cannot be compared with others on a quantitative basis. TaqI endonuclease was purified using a 5 step protocol including cell disruption, adsorption, precipitation, column chromatography and final dialysis. The enriched fraction had a specific activity of 33,600 U TaqI endonuclease per mg protein.     

Single cell protein from bagasse pith by a mixed bacterial culture

A spontaneous association of Cellulomomas sp. with another bacterial strain was studied for its capabilities for single cell protein (SCP) production from bagasse pith. The associated strain was identified as Pseudomonas sp. and further characterized for its physiological properties. The effect of the initial proportions of both strains, the way of propagation, and the effect of pH on the growth of the mixed culture on bagasse pith was studied. Separate propagation of both strains before the fermentation step (“controlled mixed culture”), a range of proportions Cellulomonas-Pseudomonas from 4:1 to 100: 1, and pH 7.0, were found to be the most appropriate conditions of growth. A mutualistic symbiotic relationship was demonstrated to take place between both strains during the mixed growth on bagasse pith, the Cellulomonas supplying the carbon source (glucose produced from bagasse degradation) to the Pseudomonas, and the latter producing the vitamin supplements necessary for the Cellulomonas growth, allowing the growth of the mixed culture in a minimal medium, without any growth factor supplement. Fed-batch cultivation of the mixed culture on this substrate was successful, giving rise to high biomass production (19.4 g/l), thus increasing the productivity of the system. Due to its improved productivity, high biomass production, inexpensiveness of the culture medium, (without any vitamin supplement), and good stability, this culture presents economical advantages and constitutes an attractive choice for lignocellulosic substrate utilization.     

Isolation of a mutant strain of Pseudomonas sp ATCC 31461 exhibiting elevated polysaccharide production

A mutant strain of the bacterium Pseudomonas sp. ATCC 31461 that exhibited elevated production of the polysaccharide gellan on glucose or corn syrup as a carbon source was isolated. Gellan production by the mutant strain was about twofold higher than its parent strain on glucose or corn syrup after 48 h of growth, and about 1.4-fold higher after 72 h. An increase in biomass production was not correlated with enhanced gellan synthesis by the mutant strain. The increased gellan production by the mutant strain on either carbon source resulted in an increase in its culture medium viscosity and the viscosity of the isolated polysaccharide produced by glucose-grown cells. No differences in the glucuronic acid content of the polysaccharides produced by the mutant and parent strains were observed. Journal of Industrial Microbiology & Biotechnology (2002) 29, 185–188 doi:10.1038/sj.jim.7000278 Received 13 February 2002/ Accepted in revised form 20 May 2002     

Biodegradation of high explosive production effluent containing RDX and HMX by denitrifying bacteria

The biodegradation of high explosive production effluent containing RDX (royal demolition explosive) and HMX (high melting-point explosive) in the presence of denitrifying bacterial isolates was investigated. The effluent collected from HMX production plant containing acetic acid, ammonium nitrate and explosive residue with water and other organic nitro bodies was used. The diluted and neutralized effluent was subjected to biodegradation using Pseudomonas (HPB1) and two Bacillus (HPB2, HPB3) denitrifying bacterial isolates. Samples were analysed by HPLC for qualitative and quantitative analysis of remaining RDX and HMX. The results indicate that the HMX and RDX was biodegraded under denitrifying conditions. The isolate Pseudomonas (HPB1) was found to be an efficient biodegrading strain for HMX. However, the isolate Pseudomonas (HPB1) was found to have lower biodegradation activity for RDX as compared to the denitrifying strain Bacillus (HPB2). Denitrifying bacteria Bacillus (HPB2) was found to be the most efficient strain for the biodegradation of RDX and HMX containing effluent neutralized with sodium bicarbonate. The biotransformation activity for HMX and RDX was lower for the isolate Bacillus (HPB2) in the effluent neutralized with ammonia. Removal of nitrate from the effluent containing HMX and RDX by the three denitrifying bacteria was also studied. Denitrifying bacteria Pseudomonas (HPB1) showed the maximum nitrate reduction in the presence of both the neutralizing agents- sodium bicarbonate and ammonia.     

Resolving Genetic Functions within Microbial Populations: In Situ Analyses Using rRNA and mRNA Stable Isotope Probing Coupled with Single-Cell Raman-Fluorescence In Situ Hybridization

Prokaryotes represent one-half of the living biomass on Earth, with the vast majority remaining elusive to culture and study within the laboratory. As a result, we lack a basic understanding of the functions that many species perform in the natural world. To address this issue, we developed complementary population and single-cell stable isotope (¹³C)-linked analyses to determine microbial identity and function in situ. We demonstrated that the use of rRNA/mRNA stable isotope probing (SIP) recovered the key phylogenetic and functional RNAs. This was followed by single-cell physiological analyses of these populations to determine and quantify in situ functions within an aerobic naphthalene-degrading groundwater microbial community. Using these culture-independent approaches, we identified three prokaryote species capable of naphthalene biodegradation within the groundwater system: two taxa were isolated in the laboratory (Pseudomonas fluorescens and Pseudomonas putida), whereas the third eluded culture (an Acidovorax sp.). Using parallel population and single-cell stable isotope technologies, we were able to identify an unculturable Acidovorax sp. which played the key role in naphthalene biodegradation in situ, rather than the culturable naphthalene-biodegrading Pseudomonas sp. isolated from the same groundwater. The Pseudomonas isolates actively degraded naphthalene only at naphthalene concentrations higher than 30 μM. This study demonstrated that unculturable microorganisms could play important roles in biodegradation in the ecosystem. It also showed that the combined RNA SIP-Raman-fluorescence in situ hybridization approach may be a significant tool in resolving ecology, functionality, and niche specialization within the unculturable fraction of organisms residing in the natural environment.     

Effects of organic compounds on the degradation ofp-nitrophenol in lake and industrial wastewater by inoculated bacteria

Many microorganisms fail to degrade pollutants when introduced in different natural environments. This is a problem in selecting inocula for bioremediation of polluted sites. Thus, a study was conducted to determine the success of four inoculants to degradep-nitrophenol (PNP) in lake and industrial wastewater and the effects of organic compounds on the degradation of high and low concentrations of PNP in these environments.Corynebacterium strain Z4 when inoculated into the lake and wastewater samples containing 20 µg/ml of PNP degraded 90% of PNP in one day. Addition of 100 µg/ml of glucose as a second substrate did not enhance the degradation of PNP and the bacterium utilized the two substrates simultaneously. Glucose used at the same concentration (100 µg/ml), inhibited degradation of 20 µg of PNP in wastewater byPseudomonas strain MS. However, glucose increased the extent of degradation of PNP byPseudomonas strain GR. Phenol also enhanced the degradation of PNP in wastewater byPseudomonas strain GR, but had no effect on the degradation of PNP byCorynebacterium strain Z4.Addition of 100 µg/ml of glucose as a second substrate into the lake water samples containing low concentration of PNP (26 ng/ml) enhanced the degradation of PNP and the growth ofCorynebacterium strain Z4. In the presence of glucose, it grew from 2×10⁴ to 4×10⁴ cells/ml in 3 days and degraded 70% of PNP as compared to samples without glucose in which the bacterium declined in cell number from 2×10⁴ to 8×10³ cells/ml and degraded only 30% PNP. The results suggest that in inoculation to enhance biodegradation, depending on the inoculant, second organic substrate many play an important role in controlling the rate and extent of biodegradation of organic compounds.Abbreviations PNP p-nitrophenol     

Atrazine degradation in saline wastewater by Pseudomonas sp strain ADP

Wastewater from atrazine manufacturing plants contains large amounts of residual atrazine and atrazine synthesis products, which must be removed before disposal. One of the obstacles to biological treatment of these wastewaters is their high salt content, eg, up to 4% NaCl (w/v). To enable biological treatment, bacteria capable of atrazine mineralization must be adapted to high-salinity conditions. A recently isolated atrazine-degrading bacterium, Pseudomonas sp strain ADP, originally isolated from contaminated soils was adapted to biodegradation of atrazine at salt concentrations relevant to atrazine manufacturing wastewater. The adaptation mechanism was based on the ability of the bacterium to produce trehalose as its main osmolyte. Trehalose accumulation was confirmed by natural-abundance ¹H NMR spectral analysis. The bacterium synthesized trehalose de novo in the cells, but could not utilize trehalose added to the growth medium. Interestingly, the bacterium could not produce glycine betaine (a common compatible solute), but addition of 1 mM of glycine betaine to the medium induced salt tolerance. Osmoregulated Pseudomonas sp strain ADP, feeding on citrate decreased the concentration of atrazine in non-sterile authentic wastewater from 25 ppm to below 1 ppm in less than 2 days. The results of our study suggest that salt-adapted Pseudomonas sp strain ADP can be used for atrazine degradation in salt-containing wastewater. Received 26 August 1997/ Accepted in revised form 06 December 1997     

Induction of Peroxidase during Infection of Unripe Persimmon Fruit by Alternaria alternata: a Possible Quiescence Mechanism

Limited black spot symptoms (Quiescent infections) develop on persimmon fruits as Alternaria alternata hyphae penetrate the pericarp of green‐immature fruit. Inoculation of persimmon with A. alternata or treatment with a commercial preparation of purified cellulase induced similar black symptoms and higher peroxidase activity in green‐immature fruits but not in orange‐mature persimmon fruits. Both treatments induced the development of new peroxidase isoforms only in immature fruits – however, no effect was observed on polyphenoloxidase activity. A. alternata was transformed with a construct expressing green fluorescent protein (GFP). Histological analysis of hyphal development using GFP‐transformed fungi indicated that symptoms are always found ahead of the leading edge of the hyphae. We suggest that peroxidase increase, induced by the directly penetrating A. alternata, might be involved in the induction of quiescence infection by the pathogen in immature fruits.