Effect of the Inoculum Size on Carbapenem Susceptibilities of β-Lactamase-Negative,Ampicillin-Resistant <Emphasis Type="Italic">Haemophilus influenzae</Emphasis>

A higher inoculum size of β-lactamase-positive Haemophilus influenzae is reported to increase minimum inhibitory concentrations (MICs) for β-lactams. However, the effect of inoculum size of β-lactamase-negative, ampicillin-resistant H. influenzae (BLNAR) on MICs for carbapenems has not been investigated. This study evaluated the effect of inoculum size on MICs for carbapenems and other β-lactams in nine clinical isolates of BLNAR. The MICs were determined by both the standard method described by the Clinical and Laboratory Standards Institute (final inoculum size of 5 × 10⁵ colony-forming units [CFU]/ml) and a modified method (final inoculum size of 5 × 10⁶ CFU/ml) using viable cell counts. The findings showed that the higher inoculum size increased MICs for imipenem, meropenem, panipenem, biapenem, ampicillin, ceftazidime, and ceftriaxone. The inoculum effect (4 log₂ dilution or a greater increase in the MIC) with imipenem, meropenem, panipenem, and biapenem was found in three, five, two, and two isolates, respectively. The magnitude of the inoculum effect for panipenem significantly increased with the levels of MICs, but correlation between them for the others was not statistically significant. The mutations of penicillin-binding protein genes had little relevance to the reduced susceptibility to carbapenems or to the magnitude of the inoculum effect. These results suggest that MIC determination using turbidity can produce interpretive errors in the antimicrobial susceptibility testing of BLNAR for carbapenems because of their inoculum effect. Thus, accurate adjustment of inoculum size, such as viable cell count, is helpful for confirming the true MICs when the isolates are interpreted as “resistant” by turbidity-based MIC determination.     

Influence of inoculum density on population dynamics and dauer juvenile yields in liquid culture of biocontrol nematodes Steinernema carpocapsae and S. feltiae (Nematoda: Rhabditida)

For improvement of mass production of the rhabditid biocontrol nematodes Steinernema carpocapsae and Steinernema feltiae in monoxenic liquid culture with their bacterial symbionts Xenorhabdus nematophila and Xenorhabdus bovienii, respectively, the effect of the initial nematode inoculum density on population development and final concentration of dauer juveniles (DJs) was investigated. Symbiotic bacterial cultures are pre-incubated for 1 day prior to inoculation of DJs. DJs are developmentally arrested and recover development as a reaction to food signals provided by their symbionts. After development to adults, the nematodes produce DJ offspring. Inoculum density ranged from 1 to 10 × 10³ DJ per milliliter for S. carpocapsae and 1 to 8 × 10³ DJs per milliliter for S. feltiae. No significant influence of the inoculum density on the final DJ yields in both nematode species was recorded, except for S. carpocapsae cultures with a parental female density <2 × 10³ DJs per milliliter, in which the yields increased with increasing inoculation density. A strong negative response of the parental female fecundity to increasing DJ inoculum densities was recorded for both species with a maximum offspring number per female of >300 for S. carpocapsae and almost 200 for S. feltiae. The compensative adaptation of fecundity to nematode population density is responsible for the lack of an inoculum (or parental female) density effect on DJ yields. At optimal inoculation density of S. carpocapsae, offspring were produced by the parental female population, whereas S. feltiae always developed a F1 female population, which contributed to the DJ yields and was the reason for a more scattered distribution of the yields. The F1 female generation was accompanied by a second peak in X. bovienii density. The optimal DJ inoculum density for S. carpocapsae is 3–6 × 10³ DJs per milliliter in order to obtain >10³ parental females per milliliter. Density-dependent effects were neither observed on the DJ recovery nor on the sex ratio in the parental adult generation. As recovery varied between different batches, assessment of the recovery of inoculum DJ batches is recommended. S. feltiae was less variable in DJ recovery usually reaching >90%. The recommended DJ inoculum density is >5 × 10³ DJs per milliliter to reach >2 × 10³ parental females per milliliter. The mean yield recorded for S. carpocapsae was 135 × 10³ and 105 × 10³ per mililiter for S. feltiae.     

Degradation of p-nitrophenol and pentachlorophenol mixtures by Sphingomonas sp. UG30 in soil perfusion bioreactors

The degradation of mixtures of pentachlorophenol (PCP) and p-nitrophenol (PNP) were evaluated in pure cultures of Sphingomonas sp. UG30, statically incubated soils (60% water-holding capacity) and soil perfusion bioreactors where encapsulated cells of UG30 were used as a soil inoculant. In pure-culture studies, conditions were optimized for mineralization of PCP and PNP mixtures at concentrations of 30 mg l⁻¹ each. Optimum in vitro mineralization of PCP and PNP mixtures by UG30 was facilitated using ammonium phosphate as a nitrogen source, while inhibition was observed with ammonium nitrate. The bioreactor system used columns containing soil treated with mixtures of 100, 225 or 500 mg kg⁻¹ of PCP and PNP. Rapid dissipation of both substrates was observed at the 100 mg kg⁻¹ level. Inoculation with UG30 enhanced PCP degradation at the 100 mg kg⁻¹ level in bioreactors but not in static soil microcosms. At higher PCP and PNP concentrations (225 mg kg⁻¹), occasional complete degradation of PNP was observed, and PCP degradation was about 80% compared to about 25% in statically incubated soils after 20 days at 22°C. There was no additional degradation of the PCP and PNP mixtures attributable to inoculation with encapsulated cells of UG30 in either soil system at concentrations of 225 or 500 mg kg⁻¹. Journal of Industrial Microbiology & Biotechnology (2000) 25, 93–99. Received 25 February 2000/ Accepted in revised form 07 June 2000     

Toxicity assessment of paraverine hydrochloride and papaverine-derived metabolites in primary cultures of rat hepatocytes

Summary The present study was undertaken to assess and compare the toxic effects of papaverine hydrochloride and its metabolites. Primary cell cultures of rat hepatocytes were treated with papavarine (papaver), 3′-O-desmethyl (3′-OH), 4′-O-desmethyl (4′-OH), and 6-O-desmethyl (6-OH) papaverine at 1×10⁻⁵, 1×10⁻⁴, and 1×10⁻³ M for 4,8, 12, and 24-h periods. Cell injury was determined by: a) cell viability using the trypan blue exclusion test; b) cytosolic enzyme leakage of lactate dehydrogenase and aspartate aminotransferase; c) morphologic alterations; and d) lactate: pyruvate (L:P) ratios. Cell cultures showed concentration-and time-dependent responses. For example, a decrease in cell viability and an increase in enzyme leakage were observed after cell treatment with 1×10⁻⁴ and 1×10⁻³ M papaver for 8 h; 1×10⁻³ M 6-OH papaverine for 8 h and 1×10⁻⁴ M for 24 h; and 1×10⁻³ M 4′-OH papaverine for 24 h (P<0.05). Furthermore, changes in morphology correlated to cell viability and enzyme release in those cultures treated with papaver, 4′-OH and 6-OH papaverine. Some of these changes included size deformation, cell detachment from the dishes, and cell necrosis. On the other hand, an increase in L:P ratios (P<0.05) was detected with papaver as early as 8 h with 1×10⁻⁴ and 1×10⁻³ M and 12 h with 1×10⁻⁵ M; 6-OH showed an increase, in L:P ratios at 8 h with 1×10⁻³ M and 12 h with 1×10⁻⁴ M; these changes were evident with 4′-OH at 12 h with 1×10⁻³ M. In contrast, cells treated with 3′-OH papaverine did not show significant damage with any time period and concentration used in this study. The results of this study indicate that papaverine-derived metabolites are less cytotoxic than its parent compound, papaver. The toxicity was ranked as follows: papaver>6-OH>4′-OH>−3′-OH. This work was supported in part by grant ES04200-02 from the National Institute of Environmental Health Sciences, Bethesda, MD. Presented in part at the fall ASPET meeting in Salt Lake City, August, 1989. Daniel Acosta is a Burroughs Wellcome Scholar in Toxicology.     

Biological effects of low-energy C ion implantation on sesame ( Sesamum indicum L.)

Field cultivation experiments on white sesame (Sesamum indicum L.) seeds implanted with low-energy C ion showed that different dosages of C ion implantation produce different biological effects. Sesame plants in 6 different dosage groups with C ion density respectively at 1 × 10¹¹, 1 × 10¹², 1 × 10¹⁵, 5 × 10¹⁵, 1 × 10¹⁶, 5 × 10¹⁶ ion/cm² were superior to the control group in plant height, leaf number, stalk diameter and leaf size. Further, sesame plants in these groups flower and seed earlier than those in the control group, and single plant yield also increased. Of all the groups, the 5 × 10¹⁵ ion/cm² dosage group yielded the best effect, whereas the 1 × 10¹⁷/cm² dosage group showed an evident inhibitory effect of ion implantation on the germination and growth of the sesame seeds. __________ Translated from Journal of Beijing Normal University (Natural Science), 2006, 42 (1): 95–97 [译自: 北京师范大学学报 (自然科学版)]     

The effect of organic toxicants on sensitivity of intestinal glycosidases to Cu and Zn in juvenile roach

The chronic effect (duration of exposure 218 days) of polychlorinated biphenyls (PCBs) and the prolonged effect of the short-term action of chlorophos or of N-methyl-N′-nitro-N-nitrosoguanidine (MNNG) during embryogenesis upon the sensitivity of intestinal glycosidases to Cu and Zn was studied in roach (Rutilus rutilus (L.) underyearlings. The Cu⁺² and Zn⁺² ions at concentrations ranging from 0.1 to 25 mg/L in vitro cause a 10–77% decrease in amylolytic activity in the intestinal mucosa of control roach. An elevated level of PCBs (50.8 ng/g wet weight of food and 426 ng/g dry weight of ground) increased the sensitivity of glycosidases to Cu and Zn. The embryotoxic action of chlorophos at concentrations of 1 × 10⁻⁶−1 × 10⁻² mg/L in most cases increased the inhibitory effect of Cu but decreased that of Zn. As a rule, MNNG (3 × 10⁻⁷−3 × 10⁻¹ mg/L) reduced the glycosidase sensitivity to the effect of metal ions. The magnitude and direction of the effect depend on the nature and concentration of toxicants.     

Kinetics and mechanism of tolerance induction on acclimation ofVillorita cyprinoides (Hanley) to copper and zinc

The typical euryhaline clamVillorita cyprinoides (Hanley) was acclimated to copper and zinc at salinity 13 × 10⁻³ and < 1 × 10⁻³ (fresh water). Acclimation enhanced the lethal tolerance, as denoted by dose-survival curves, which was more pronounced after zinc acclimation. In fresh water copper acclimation sensitized the organisms. The copper accumulation trend was significantly changed consequent to metal acclimation, especially after zinc acclimation, indicating some tissue metal regulatory effect. Acclimation to copper equiped the organism to survive for longer periods with increased body burden of copper, while zinc acclimation supressed the uptake of the more toxic ion copper. The earlier report of increased uptake of zinc by this organism during combined exposure with copper is corelated in the present context. The role of metallothionein like protein in providing protection against metal toxicity, the environmental implication of acclimation phenomena are indicated     

Production of inulinase by solid-state fermentation: effect of process parameters on production and preliminary characterization of enzyme preparations

This work was aimed at producing inulinase by solid-state fermentation of sugarcane bagasse, using factorial design to identify the effect of corn steep liquor (CSL) and soybean bran concentration, particle size of bagasse and size of inoculum. Maximum inulinase activity achieved was 250 U per g of dry substrate (gds) at 20% (w/w) of CSL, 5% (w/w) of soybean bran, 1 × 10¹⁰ cells mL⁻¹ and particle size of bagasse in the range 9/32 mesh. The use of soybean bran decreased the time to reach maximum activity from 96 to 24 h and the maximum productivity achieved was 8.87 U gds⁻¹ h⁻¹. The maximum activity was obtained at pH 5.0 and 55.0°C. Within the investigated range, the enzyme extract was more thermostable at 50.0°C, showing a D-value of 123.1 h and deactivation energy of 343.9 kJ gmol⁻¹. The extract showed highest stability from pH 4.5 to 4.8. Apparent K _m and V _max are 7.1 mM and 17.79 M min⁻¹, respectively.     

Use of quantitative real-time PCR to monitor population dynamics of ammonia-oxidizing bacteria in batch process

A quantitative real-time PCR (QPCR) assay with the TaqMan system was used to quantify 16S rRNA genes of β-proteobacterial ammonia-oxidizing bacteria (AOB) in a batch nitrification bioreactor. Five different sets of primers, together with a TaqMan probe, were used to quantify the 16S rRNA genes of β-proteobacterial AOB belonging to the Nitrosomonas europaea, Nitrosococcus mobilis, Nitrosomonas nitrosa, and Nitrosomonas cryotolerans clusters, and the genus Nitrosospira. We also used PCR followed by denaturing gradient gel electrophoresis (DGGE), cloning, and sequencing of their 16S rRNA genes to identify the AOB species. Seed sludge from an industrial wastewater treatment process controlling high-strength nitrogen wastewater (500 mg/L NH₄ ⁺–N) was used as the inoculum for subsequent batch experiment. The Nitrosomonas nitrosa cluster was the predominant AOB (2.3 × 10⁵ copies/mL) in the start-up period of the batch experiment. However, from the exponential growth period, the Nitrosomonas europaea cluster was the most abundant AOB, and its 16S rRNA gene copy number increased to 8.9 × 10⁶ copies/mL. The competitive dominance between the two AOB clusters is consistent with observed differences in ammonia tolerance and substrate affinity. Analysis of the DGGE results indicated the presence of Nitrosomonas europaea ATCC19718 and Nitrosomonas nitrosa Nm90, consistent with the QPCR results.     

Body and scale growth of wild Atlantic salmon smolts during seaward emigration

The relationship between scale and body growth for emigrating Atlantic salmon, Salmo salar, smolts was previously not understood and therefore was examined in this study using mark-recapture techniques. The size of smolts at time of recapture was significantly greater than when marked (P = 0.0002). The growth in length of smolts emigrating 5 km over an average of 20 days was 7.7 ± 6.1 mm per day. Instantaneous somatic growth (G _body) ranged from 7.0 × 10⁻⁴ to 5.1 × 10⁻³ (mean = 2.7 × 10⁻³ ± 1.3 × 10⁻³). The mean number of plus growth circuli present per scale was significantly greater for smolts when recaptured compared to when marked (P = 0.0014). The instantaneous growth rate of scales (G _scale) ranged from 1.4 × 10⁻³ to 11.5 × 10⁻³ (mean = 6.6 × 10⁻³ ± 4.3 × 10⁻³). The relationship between body size and scale radius showed positive allometry rather than isometry. The relationship of G _scale with G _body showed positive allometry indicating that scales grew at a slightly faster rate than the body during the emigratory period.     

Spore-forming bacteria in soil cultivated with GM white poplars: Isolation and characterization

The impact of transgenic white poplars (Populus alba L. cv. ‘Villafranca’) was assessed on the soil aerobic spore-forming bacteria (SFB). The genetically modified poplars, expressing either the StSy gene for resveratrol production or the bar gene for herbicide tolerance, were cultivated in greenhouse. The occurrence of SFB was monitored in soil samples collected at eight different timepoints over a two-year period. The total culturable bacterial population of the StSy and bar trials underwent significant seasonal fluctuations in the range of 10⁶−2.5 × 10⁸ CFU/g dry soil and of 10⁴−5 × 10⁸ CFU/g dry soil, respectively. Changes occurred also within the culturable SFB population with size varying at 10³−5 × 10⁴ CFU/g dry soil and 10²−2 × 10⁵ CFU/g dry soil in the StSy and bar trials, respectively. No significant differences in the size of the total and SFB culturable populations were observed when comparing each transgenic line with the nontransformed control line while seasonal shifts of soil bacterial populations were evident in both trials. The culturable SFB fraction included three isolates (SFB-1, SFB-2 and SFB-3) classified by 16S rDNA sequence analysis as members of the Bacillus genus. According to the reported data, cultivation of both herbicide-resistant and resveratrol-producing GM white poplars did not affect the culturable SFB population at the soil level.     

Effect of two microalgae concentrations on body size and egg size of the rotifer <Emphasis Type="Italic">Brachionus calyciflorus</Emphasis>

The rotifer, Brachionus calyciflorus, was grown with two algae species (Chlorella sp. and Scenedesmus obliquus) at different concentrations (0.1, 1 and 10 × 10⁶ cells ml⁻¹). The body size (lorica biovolume) of individual rotifer and their egg size were measured when the populations were roughly in the exponential phase of population growth. The body size of the rotifers differed significantly (P < 0.05) among the two algae species used, however this effect was not observed for egg size. The body size of rotifers fed on higher densities of Chlorella sp. (10 × 10⁶ cells ml⁻¹) was significantly larger than for those fed on lower and medium densities (0.1 and 1 × 10⁶ cells ml⁻¹). Body size and egg size of rotifers fed with different amounts of Scenedesmus did not differ significantly. The egg size was significantly larger at higher food level of Chlorella. A significantly positive correlation was observed between the adult rotifer body size and their egg size.     

Studies on the production of nigerloxin using agro-industrial residues by solid-state fermentation

Nigerloxin, a new and potent lipoxygenase inhibitor, was discovered in our laboratory through solid-state fermentation of wheat bran by Aspergillus niger V. Teigh (MTCC-5166). The aim of this study is to investigate the possibility of using different agro-industrial residues as nutritional supplements along with wheat bran to enhance the production of nigerloxin. Nigerloxin produced by SSF was quantified spectrophotometrically at 292 nm. The results indicate that the inhibitor production was influenced by the type of solid substrate supplemented, moisture content, pH and size of the inoculum. Individually optimized supplements were tested in different combinations to determine their effects on nigerloxin production. A twofold increase in the production of nigerloxin (4.9 ± 0.3 mg gds⁻¹) was achieved by supplementing wheat bran with 10% w/w sweet lemon peel and 5% v/w methanol at optimized process parameters, that is, an initial moisture content of 65% v/w and incubation period of 6 days with an initial inoculum size of 2 ml (8 × 10⁵ spores gds⁻¹). Nigerloxin production was stable between pH of 4 and 5.     

Use of clove oil to anaesthetize freshwater amphipods

The use of clove oil as a potential anaesthetic for freshwater amphipods was examined at 20 °C. Individuals of Gammarus minus, a common species in southern Illinois, USA, spanning the entire body size range (4.3–14.3 mm), were used to test four anaesthetic concentrations varying from 1.48 × 10⁻⁴ ml ml⁻¹ to 5.9 × 10⁻⁴ ml ml⁻¹. Small-bodied individuals (mean size = 5.4 mm ± 0.27SE) were used to test additional concentrations, up to 14.7 × 10⁻⁴ ml ml⁻¹, a 10-fold span, to identify potential lethal concentrations. At the lowest concentration, time to anaesthesia and recovery was constant at all body sizes. For the three next higher concentrations, time to anaesthesia decreased with increasing concentration while recovery time increased. Activity of amphipods was not affected by the ethanol carrier. In addition, activity did not differ between amphipods that had recovered from anaesthesia and unexposed amphipods. At clove oil concentrations of 8.84 × 10⁻⁴ ml ml⁻¹ and 14.7 × 10⁻⁴ ml ml⁻¹, mortality was 7 and 40%, respectively, indicating, that 5.9 × 10⁻⁴ ml ml⁻¹ was a safe working concentration. No mortality was observed with Gammarus acherondytes, a federally endangered cave amphipod on which the protocol with 80 μl of stock was used in the field. The method enabled us to obtain information on the endangered amphipod which normally would have required the sacrifice of individuals. Thus, research can continue on species for which population numbers are low and for which basic information is needed to formulate meaningful recovery plans.     

Auxin synthesis by the higher fungus Lentinus edodes (Berk.) sing in the presence of low concentrations of indole compounds

The auxin formation in a submerged culture of the xylotrophic basidiomycete Lentinus edodes (Berk.) Sing (Lentinula edodes (Berk.) Pegler) (shiitake) is studied. Biologically active substances of an indole nature are identified, “the effect of small doses” of which lies in not only the stimulation of growth of the mycelium (indole-3-acetic acid, 2 × 10⁻⁷–2 × 10⁻⁴ g/l), but also in the induction of tryptophan-independent paths of auxin biosynthesis. The above-mentioned path is realized in the presence of exogenous indole (1 × 10⁻³–1 × 10⁻⁴ g/l), as well as while inducing the biosynthesis of indole-3-acetic acid by its microadditives (1 × 10⁻⁵−1 × 10⁻⁸ g/l), and is accompanied by the formation of anthranilic acid (up to 1.5 mg/l). Induction of the generative development stage of shiitake by indole derivatives is revealed. It was found that among the studied compounds only indoleacetamide at a concentration of an order of ×10⁻⁴ g/l in the culture fluid of L. edodes had a pronounced stimulatory effect on the formation of shiitake’s brown mycelial film.     

Explanations for the acclimation period preceding the mineralization of organic chemicals in aquatic environments

A study was conducted of possible reasons for acclimation of microbial communities to the mineralization of organic compounds in lake water and sewage. The acclimation period for the mineralization of 2 ng of p-nitrophenol (PNP) or 2,4-dichlorophenoxyacetic acid per ml of sewage was eliminated when the sewage was incubated for 9 or 16 days, respectively, with no added substrate. The acclimation period for the mineralization of 2 ng but not 200 ng or 2 micrograms of PNP per ml was eliminated when the compound was added to lake water that had been first incubated in the laboratory. Mineralization of PNP by Flavobacterium sp. was detected within 7 h at concentrations of 20 ng/ml to 2 micrograms/ml but only after 25 h at 2 ng/ml. PNP-utilizing organisms began to multiply logarithmically after 1 day in lake water amended with 2 micrograms of PNP per ml, but substrate disappearance was only detected at 8 days, at which time the numbers were approaching 10(5) cells per ml. The addition of inorganic nutrients reduced the length of the acclimation period from 6 to 3 days in sewage and from 6 days to 1 day in lake water. The prior degradation of natural organic materials in the sewage and lake water had no effect on the acclimation period for the mineralization of PNP, and naturally occurring inhibitors that might delay the mineralization were not present. The length of the acclimation phase for the mineralization of 2 ng of PNP per ml was shortened when the protozoa in sewage were suppressed by eucaryotic inhibitors, but it was unaffected or increased if the inhibitors were added to lake water.(ABSTRACT TRUNCATED AT 250 WORDS)     

Explanations for the acclimation period preceding the mineralization of organic chemicals in aquatic environments.

A study was conducted of possible reasons for acclimation of microbial communities to the mineralization of organic compounds in lake water and sewage. The acclimation period for the mineralization of 2 ng of p-nitrophenol (PNP) or 2,4-dichlorophenoxyacetic acid per ml of sewage was eliminated when the sewage was incubated for 9 or 16 days, respectively, with no added substrate. The acclimation period for the mineralization of 2 ng but not 200 ng or 2 micrograms of PNP per ml was eliminated when the compound was added to lake water that had been first incubated in the laboratory. Mineralization of PNP by Flavobacterium sp. was detected within 7 h at concentrations of 20 ng/ml to 2 micrograms/ml but only after 25 h at 2 ng/ml. PNP-utilizing organisms began to multiply logarithmically after 1 day in lake water amended with 2 micrograms of PNP per ml, but substrate disappearance was only detected at 8 days, at which time the numbers were approaching 10(5) cells per ml. The addition of inorganic nutrients reduced the length of the acclimation period from 6 to 3 days in sewage and from 6 days to 1 day in lake water. The prior degradation of natural organic materials in the sewage and lake water had no effect on the acclimation period for the mineralization of PNP, and naturally occurring inhibitors that might delay the mineralization were not present. The length of the acclimation phase for the mineralization of 2 ng of PNP per ml was shortened when the protozoa in sewage were suppressed by eucaryotic inhibitors, but it was unaffected or increased if the inhibitors were added to lake water.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cyanobacterial akinete induction and its application as biofertilizer for rice cultivation

Nostoc sp. VICCR1-1 was induced in order to form akinetes on the basis of nutrient modification. Phosphorus and iron were found to be the critical for akinete differentiation, especially when both elements were omitted. The number of akinete cells increased up to 20% when compared with culturing in BG11₀ medium (without N source). In addition, CaCl₂ played a role in heterocyst differentiation, and was able to induce heterocyst ranging between 30% and 46%. In order to prepare akinetes as inoculum, the dried form of akinetes was prepared by mixing it with montmorillonite clay. The inoculum with the amount of 2.8 × 10⁶ cells m⁻² was applied to rice (Oryza sativa) fields. After harvesting, the grain yields from chemical N fertilizer, vegetative cells, and akinete inoculum treatments were not significantly different. To monitor the persistence of Nostoc sp. VICCR1-1 after harvesting, the most probable number-denaturing gradient gel electrophoresis technique using 16S rRNA gene was employed. The results indicated that the remaining population is at 2.5 × 10⁵ and 1.62 × 10⁶ cells m⁻² in treatments supplied with vegetative cells and akinete inocula, respectively. Akinete induction might be one of the appropriate approaches for producing cyanobacterial inoculum.     

A Mutant of Metarhizium anisopliae var. acridum with Enhanced Submerged Conidiation

Summary An insertional mutant of Metarhizium anisopliae is described with enhanced submerged conidiation. In a 500 ml submerged culture, this mutant produces a mean of 4.05 × 10⁸ propagules ml⁻¹ from an inoculum of 1 × 10⁶ conidia, where the parental strain accumulates only 3.75 × 10⁴ propagules ml⁻¹.     

Statistical optimization for tannase production from <Emphasis Type="Italic">Aspergillus niger</Emphasis> under submerged fermentation

Statistically based experimental design was employed for the optimization of fermentation conditions for maximum production of enzyme tannase from Aspergillus niger. Central composite rotatable design (CCRD) falling under response surface methodology (RSM) was used. Based on the results of ‘one-at-a-time’ approach in submerged fermentation, the most influencing factors for tannase production from A. niger were concentrations of tannic acid and sodium nitrate, agitation rate and incubation period. Hence, to achieve the maximum yield of tannase, interaction of these factors was studied at optimum production pH of 5.0 by RSM. The optimum values of parameters obtained through RSM were 5% tannic acid, 0.8% sodium nitrate, 5.0 pH, 5 × 10⁷ spores/50mL inoculum density, 150 rpm agitation and incubation period of 48 h which resulted in production of 19.7 UmL⁻¹ of the enzyme. This activity was almost double as compared to the amount obtained by ‘one-at-a-time’ approach (9.8 UmL⁻¹).