Effect of temperatures during pure culture fermentation of Kinema

Kinema was prepared by fermenting whole cooked soybeans with pure culture of Bacillus subtilis KK2:B10 (MTCC 2756) strain at 35°C, 40°C and 45°C for 24h. Temperature, mesophilic plate counts, relative viscosity, water-soluble nitrogen, formal nitrogen contents and reducing sugars of fermenting soybeans were investigated during fermentation. At higher temperatures the growth rate of B. subtilis KK2:B10 was faster. A remarkable increase in the relative viscosity of kinema was observed at 40°C during fermentation. Water-soluble nitrogen and formol nitrogen to total nitrogen contents increased throughout the 24h of fermentation. Reducing sugars increased during the log phase and then decreased sharply. Kinema matured below 10°C for 1 day after the desired fermentation showed a significant increase in relative viscosity. The quality of kinema was maintained with pure culture fermentation by B. subtilis KK2:B10 at 40°C for 20h and matured at 5°C for 1 day.     

Effect of cations, pH and sulfate content on the viscosity and emulsifying activity of the Halomonas eurihalina exopolysaccharide

The effects of monovalent and divalent cations on the rheological behavior of Halomonas eurihalina exopolysaccharide (EPS) were studied. Sodium, potassium, magnesium and calcium were added and the relative abilities to increase viscosity were as follows: KCl > NaCl > MgCl₂ > CaCl₂. The highest viscosity value was measured in acidic 10⁻⁴ M KCl, in which a gel formed. A loss of sulfate content seemed to correlate with the increase of viscosity. H. eurihalina produced EPS in all growth media. Addition of hydrophobic substrates to culture media produced changes in chemical composition and emulsifying activity of the EPS. Xylene was the most effectively emulsified substance and the EPS produced on tetradecane and on corn oil the most active emulsifier. Received 25 July 1997/ Accepted in revised form 30 January 1998     

Effect of Viscosity on Formation and Sedimentation of Polytomella agilis Vertical Aggregates*

The response of vertical aggregates of Polytomella agilis to increased viscosity of the medium indicates that viscous resistance of the medium is a critical factor controlling the formation and sedimentation of protozoan aggregates. Aggregate formation time increased from 20 sec to 6.5 min as viscosity was increased 1.72 times. Sedimentation rate decreased about 140 μm/sec for each 10% increment in viscosity. Although there was a 60% decrease in speed of falling aggregates when relative viscosity was increased from 1.0 to 1.6, individually swimming P. agilis decreased less than 22% in speed even at a relative viscosity of 1.84 where aggregates did not form. Cells continued to accumulate near the surface by negative geotactic swimming after vertical aggregation ceased. Vertical aggregation is a cyclic process composed of 4 phases: a) accumulation-aggregation; b) aggregate sedimentation; c) ablation and dispersal; and d) negative geotaxis. Phase d is unique to motile microorganisms and only in such populations is vertical aggregation continuously selfperpetuating. Phases a-c occur with both motile and nonmotile bodies and are dependent upon viscous forces of the medium.     

Filamentous cyanobacteria,temperature and <Emphasis Type="Italic">Daphnia</Emphasis> growth: the role of fluid mechanics

Viscosity increases significantly with a fall in water temperature, thus temperature change affects not only the metabolic rates of aquatic suspension feeders, but also the physical properties of the surrounding fluid. This mechanistic effect of water temperature change on growth was separated from the effect of metabolism by using culture media with modified viscosity, while the temperature was kept constant. The effect of water viscosity on growth rate and feeding of four Daphnia species (D. magna, D. pulicaria, D. hyalina, D. galeata) was investigated. Increased viscosity decreased the growth rate significantly for three species, with the exception of D. galeata. Changing viscosity also affects growth qualitatively: the filamentous blue-green Cylindrospermopsis raciborskii reduces the growth rate of D. pulicaria at low viscosity, but its negative effect disappears when viscosity is higher. The findings are consistent with the hypothesis that it is the Reynolds number of the filtering appendages that determines the qualitative features of Daphnia filtration. The edibility of C. raciborskii at high water viscosity is most probably caused by lack of interference with filtering combs, and explains the coexistence of D. pulicaria with filamentous blue-green species in the field, and also the observed temperature dependence of growth inhibition of filaments.Electronic Supplementary Material Supplementary material is available for this article at     

Rheological properties of <Emphasis Type="Italic">Chlorella pyrenoidosa</Emphasis> culture grown heterotrophically in a fermentor

Rheological properties of Chlorella pyrenoidosa culture grown heterotrophically in a 14 L fermentor were investigated. It was found that the fluid viscosity was rather low and remained almost unchanged during the cultivation, implying that no (or very few) viscous substances were excreted into the medium. Investigation of the condensed suspension of C. pyrenoidosa showed that for biomass concentration under 150 g.L⁻¹, the suspension of C. pyrenoidosa exhibited Newtonian behavior, and the fluid viscosity was rather low (about 40 mPa·s) and increased very slowly with the increase in cell concentration. With further increase in biomass concentration however, the fluid rheological behavior changed to non-Newtonian, and the fluid viscosity increased rapidly with the increase in cell concentration. From the viewpoint of rheology, C. pyrenoidosa is an excellent organism for high-cell-density culture, and there will be no rheological problems at cell densities under 150 g.L⁻¹.     

Factors affecting broth viscosity and coenzyme Q10 production by Agrobacterium species

Summary In the production of coenzyme Q₁₀ (CoQ₁₀) by Agrobacterium sp. the culture broth becomes highly viscous. In an attempt to improve the production process, the effects of chemical and physical factors on broth viscosity and CoQ₁₀ production were studied, using Agrobacterium sp. KY-8593. A particular concentration ratio of sugar to ammonium-nitrogen (NH₄–N) in the medium could effectively enhance CoQ₁₀ production without increasing broth viscosity. An increase in culture temperature to between 32°C and 34°C lowered broth viscosity without reducing CoQ₁₀ production. NH₄–N concentration and temperature had a correlative effect on broth viscosity. At a temperature of about 33°C, there was a wide range of NH₄–N concentration which was optimal for both broth viscosity and CoQ₁₀ production. In optimal conditions with 8% sugar the apparent broth viscosity was reduced to less than 10 pseudo-cP and CoQ₁₀ production was increased to more than 80 mg/l.     

Effect of unionized ammonia,viscosity and protozoan contamination on reproduction and enzyme activity of the rotifer Brachionus rotundiformis

We determined the effect of environmental stressors on the physiological condition of Brachionus rotundiformis. For two morphologically distinct B. rotundiformis strains: Hawaii (average lorica length = 222 m) and Langkawi strains (average lorica length 180 m), neonates hatched from resting eggs were exposed to different levels of unionized ammonia (0.7–9.8 mg l^–1), viscosity (relative viscosity against natural seawater = 1–1.17) and Euplotes sp. (protozoan) contamination (1–40 cells ml^–1). Increasing stress decreased fecundity and lifespan of both rotifer strains. Glucosidase and phospholipase activities were correlated with reproductive responses of both the strains exposed to unionized ammonia. When culture water viscosity was changed, the activity of esterase and phospholipase was correlated with reproductive responses of the Hawaiian strain, and glucosidase activity was correlated with those of Langkawi strain.With the protozoan contamination, esterase and glucosidase activities were correlated only with reproductive responses of the Hawaiian strain, while activity of all three enzymes was correlated to those of the Langkawi strain. Glucosidase activity proved to be a reliable indicator of stress for cultured B. rotundiformis.     

A study of the rheological properties of a non-Newtonian fermentation broth

Polysaccharide was synthesized by Aureobasidium pullulans (or Pullularia pullulans) 2552 in a sucrose medium. The field apparent viscosity of the culture medium from shake flask experiments rose to 24,500 cP and then dropped toward its initial value as the fermentation progressed. The magnitude of the maximum apparent viscosity depended on the initial pH of the fermentation broth. The inoculum age influenced the cultivation period before which the maximum viscosity was reached. Rheograms of the fermentation broths showed a change in viscosity behavior from Newtonian to pseudoplastic, and then toward Newtonian characteristics during the fermentation. The calculated non-Newtonian index was found to be a sensitive factor for the indication of the non-Newtonian behavior. Such behavior could not be detected from rheograms. Viscosity profiles of polysaccharide isolated from various stages of the fermentation showed a change from Newtonian to pseudoplastic behavior depending on the concentration (0–2%) of polysaccharide.     

Rheological characterization of culture broth containing the exopolysaccharide PS-EDIV from Sphingomonas pituitosa

Sphingomonas pituitosa excretes the capsular exopolysaccharide PS-EDIV into the culture broth augmenting considerably its fluid viscosity. Since this change particularly affects key processes like mixing and transport during the microbial production, this work was aimed at the rheological characterization of the polymer-containing culture broth of S. pituitosa. The study included investigations on basic properties of the culture broth, but also on the dependence of the biomass–polymer-solution properties on different physicochemical post-cultivation treatment steps like variations of temperature, pH-value or concentration of salts. The essential result is the characterization of the viscoelastic behavior of the culture broth, which was more gel-like than sol-like and exhibited slight elastic properties. This rheological behavior showed that the PS-EDIV culture broth formed non-Newtonian fluids, indicating that it is a pseudoplastic biopolymer, with yield stress appearance and exhibits thixotropic properties. Rheograms were fitted to the Herschel–Bulkley model. The amplitude sweep revealed a deformation of 21% as the limiting value of the linear viscoelastic interval. Furthermore, the PS-EDIV culture broth showed a high viscosity which was strongly influenced by salt type and concentration but weakly influenced by temperature and pH-value within the investigated experimental boundaries.     

Competitive relationships existing between two closely related species of Argemone living in the same area

Summary The present paper deals with the reaction of two closely related species of Argemone L., A. mexicana L. and A. ochroleuca Sweet, to its own density in pure stands and a comparison of this with its reaction to the density of the associated species. The results of the pure culture studies indicate that whilst each of the two species reacted to an increase in its own density by higher mortality and a striking reduction in vegetative and reproductive growth, A. mexicana was more susceptible to intraspecific effect than A. ochroleuca. On the other hand, mixed culture studies indicated that A. mexicana was more successful when in competition with A. ochroleuca. Further, that species which was in a majority in the mixture suffered most compared to the minority species. Such a density dependent differential behaviour in pure stands and frequency dependent differential behaviour in mixed cultures along with the reversal in superiority of the two species in pure and mixed cultures was considered to be responsible for the cohabitation of the two species and their relative population sizes in nature.     

Effect of carbon dioxide on the rheological behavior of submerged cultures of Chlorella minutissima in stirred tank reactors

The objective of this study was to quantify the effect of algal biomass concentration on the rheology of the algal culture broth. Batch cultivations of Chlorella minutissima were carried out with air and carbon dioxide in a stirred tank bioreactor with a working volume of 1.8 L. The apparent viscosity of the culture broth was significantly affected by the cell mass concentrations in the bioreactor. Culture broth containing 50 g/L cell mass from air fed was found to exhibit an apparent viscosity of 1.52 mPa.s. The apparent viscosity of the carbon‐dioxide‐fed cultivations was found to increase by 20% at a shear rate of 100 s^?1. The flow behavior of the system was adequately described by the Herschel–Bulkley model with a small yield stress.     

A natural terrestrial biofilm

Material recovered from an extensive and viscous biofilm found on areas of rough hill pasture in Southern Scotland proved to consist of a thick mucilaginous deposit of polysaccharide in which species of green algae, withGleocystis spp as the dominant microorganism and lesser numbers ofOocystis spp. Cyanobacteria were also entrapped. On laboratory culture other green algal and cyanobacterial species were detected. Analysis of the native polysaccharide and of the exopolysaccharide from a mixed culture of the dominant algal species derived from the original material, revealed the major components as glucose, galactose, mannose and rhamnose. The content of uronic acids was very low. The viscosity of the polysaccharide preparations was determined and compared with bacterial biofilm material; viscosity was lost following phenol extraction indicating that the original material was probably closely associated with proteins.     

Combined dissolved oxygen tension and online viscosity measurements in shake flask cultivations via infrared fluorescent oxygen-sensitive nanoparticles

Oxygen supply is one of the most critical process parameters in aerobic cultivations. To assure sufficient oxygen supply, shake flasks are usually used in combination with orbital shaking machines. In this study, a measurement technique for the dissolved oxygen tension (DOT) in shake flask cultures with viscosity changes is presented. The movement of the shaker table is monitored by means of a Hall effect sensor. For DOT measurements, infrared fluorescent oxygen-sensitive nanoparticles are added to the culture broth. The position of the rotating bulk liquid needs to be determined to assure measurements inside the liquid. The leading edge of the bulk liquid is detected based on the fluorescence signal intensity of the oxygen-sensitive nanoparticles. Furthermore, online information about the viscosity of the culture broth is acquired due to the detection of the position of the leading edge of the bulk liquid relative to the direction of the centrifugal force, as described by Sieben et al. (2019. Sci. Rep., 9, 8335). The DOT measurement is combined with a respiration activity monitoring system which allows for the determination of the oxygen transfer rate (OTR) in eight parallel shake flasks. Based on DOT and OTR, the volumetric oxygen transfer coefficient (k_La) is calculated during cultivation. The new system was successfully applied in cultivations of Escherichia coli, Bacillus licheniformis, and Xanthomonas campestris.     

Reduction ofRenibacterium salmoninarumculture activity in Atlantic salmon following vaccination with avirulent strains

A series of challenge experiments were conducted to determine the efficacy of vaccination against bacterial kidney disease (BKD) in Atlantic salmon using an avirulent mutant ofRenibacterium salmoninarum(RsTSA I), and a related Gram-positive bacterium (Rsx II). Vaccination had a pronounced effect on the presence of the pathogen in fish kidney tissue. At 14 weeks after infection, the relative percentage of fish which were culture negative forR. salmoninarumwas 69·0 and 81·2 respectively for the two strains compared to 85·8% culture positive for the unvaccinated control group. Furthermore the use of a polymerase chain reaction (PCR) test to detectR. salmoninarumbeing shed from the asymptomatic fish clearly identified the pathogen in water from tanks containing the unvaccinated group but not from water taken from the tanks vaccinated with either of the vaccine strains.     

Effect of aeration and carbon/nitrogen ratio on the molecular mass of the biodegradable polymer poly-β-hydroxybutyrate obtained from Azotobacter chroococcum 6B

The bacterial polyester poly-β-hydroxybutyrate (PHB) was quantified and characterized on an isolate␣of the nitrogen-fixing bacteria Azotobacter chroococcum 6B on the basis of its average molecular mass, determined from the relative viscosity at different aeration rates and carbon/nitrogen ratios during culture in fermentors. A higher value for the molecular mass (1100 kDa) was obtained with the lower aeration rates investigated, which diminished, significantly at the highest aeration rate of 2.5 vvm (a 100-fold decrease). The yield of PHB relative to the amount of glucose consumed increased with the C/N ratio (a maximum of 0.16 g PHB/g glucose consumed with a carbon/nitrogen ratio of 137.7), but the molecular mass was lowered from 800 kDa to nearly 100 kDa. The maximum PHB content was 63.5% (on a cellular dry-weight basis) after 47 h in fed-batch culture with an initial C/N ratio of 68.9 and aeration at a rate of 0.5 vvm. Calorimetric measurements on the isolated PHB showed a melting point near 175 °C. Received: 25 June 1997 / Accepted: 2 July 1997     

Effect of aeration rates on production of extracellular polysaccharide, EPS-R, by marine bacteriumHahella chejuensis

The production of an extracellular polysaccharide, EPS-R, from the marine bacteriumHahella chejuensis was investigated at various aeration rates in a batch culture. Higher aeration rate resulted in enhanced EPS production and increased the viscosity of the culture broth. At an aeration rate of 1.5 vvm, EPS-R (12.2 g/L) was obtained with a yield (Y _P/S) of 0.6 from the STN medium after 72h of cultivation. TheH. chejuensis cells changed their rod morphology to a short-rod form in the stationary growth phase.     

Stimulation of citric acid production in Aspergillus niger by addition of viscous substances in shake culture

When glucose (120mg/ml) was used as a carbon source, Aspergillus niger Yang no. 2. showed a markedly low citric acid productivity in shake culture (15.4 mg/ml) but a high productivity in semi-solid and surface cultures (72.3 mg/ml and 67.6 mg/ml, respectively). Since the viscosity of the medium was assumed to be one of the important factors for citric acid productivity in shake culture, the effects of the addition of viscous substances on citric acid productivity of strain Yang no. 2 were examined. The addition of 2.0–6.0 mg gelatin/ml as a viscous additive to the medium containing glucose as a carbon source increased slightly the medium viscosity but substantially increased the citric acid productivity in shake culture to levels of 52.0–53.3 mg/ml, about 3.4 times as much as that without gelatin. However, no influence of gelatin addition was observed in semi-solid and surface cultures, i.e. under static cultivation conditions. Different mycelial morphologies of the strain were observed when cultivations were done in shake culture with or without the addition of gelatin. Addition of 5.0 mg agar/ml, 5.0 mg carageenan/ml, 2.5 mg carboxymethylcellulose/ml and 2.5 mg polyethylene glycol 6000/ml, to the medium containing glucose as a carbon source also increased the citric acid productivity in shake culture to levels of 39.2–54.7 mg/ml. Since Yang no. 2 does not utilize these viscous substances, these results suggested that the viscous substances functioned as protectants for the mycelium from physiological stresses due to shaking and as a consequence resulted in a remarkably increased citric acid productivity in shake culture.     

Characterization of the Extracellular Polysaccharide Produced by a Marine Cyanobacterium, Cyanothece sp. ATCC 51142, and Its Exploitation Toward Metal Removal from Solutions

Cyanobacterium, Cyanothece sp. ATCC 51142 produces an exopolysaccharide at a high level. Physical analysis of the exopolysaccharide (EPS), such as nuclear magnetic resonance, infrared spectrum, were done to determine its possible structure. Thermal gravimetric analysis, differential scanning calorimeter, and differential thermal analysis of the polymer were done to find out the thermal behavior. Calcium content within the sample was found out. Some of the physicochemical properties, such as relative viscosity, specific viscosity, and intrinsic viscosity of the EPS were studied under different conditions. The phenomenon of gel formation by the EPS was investigated for its potential application in metal removal from solutions. Received: 23 August 1999 / Accepted: 12 November 1999     

Norms of reaction and diversifying selection

The numbers of progeny produced by comparable numbers of female Drosophila melanogaster of 26 geographic strains on nine different culture media are examined in the context of norms of reaction. Having emphasized that diversifying selection is seldom discussed simultaneously with its seemingly related topic, norms of reaction, I present the following argument: diversifying selection has generally been viewed as involving sub-populations inhabiting separate localities and subject to different patterns of selection, norms of reaction as variation whose weighted average determines the relative fitnesses of different genotypes within individual sub-populations. Should environmental challenges frequently involve life or death (including sterility) outcomes, norms of reaction involving components of fitness engender diversifying selection within local populations (demes).     

Production and Characterization of an Exopolysaccharide by Yeast

Antarctic yeast strains were investigated for exopolysaccharide biosynthesis and the Sporobolomyces salmonicolor AL₁ strain was selected. It was studied for exopolysaccharide biosynthesis on different carbon and nitrogen sources. The investigations showed that sucrose and ammonium sulphate were suitable culture medium components for polymer biosynthesis. Exopolysaccharide formation by the yeast strain was accompanied by a decrease in the culture medium pH value from the initial pH 5.3 to pH 1.7–2.0. During the biosynthetic process, the dynamic viscosity of the culture broth increased to the maximum value of 15.37 mPas and the polysaccharide yield reached 5.63 g/l on a culture medium containing 5.00% sucrose and 0.25% ammonium sulphate at a temperature of 22 °C for 120 h. The crude polysaccharide obtained from Sp. salmonicolor AL₁ featured high purity (90.16% of carbon content) and consisted of glucose (54.1%), mannose (42.6%) and fucose (3.3%). Pure mannan containing 98.6% of mannose was isolated from it.