Bacterial Biomass Concentration Research Articles

Can heavy metal pollution stress reduce microbial carbon-use efficiencies?

The fate of soil organic matter (OM) is determined by its microbial use for growth or respiration. Many environmental factors influence microbial OM use, including the presence of contaminants and toxins in the environment, such as heavy metals. We evaluated short- and long-term responses of microbial processes to metal contamination by estimating biomass concentrations and growth rates of bacteria and fungi, respiration, and the resulting microbial carbon-use efficiencies (CUE), and microbial turnover times. We sampled O-horizon from a gradient in boreal forest soils exposed to long-term heavy metal contamination arising from industrial point source since the 1930s to assess long-term effects on soil microorganisms. To estimate microbial responses to short-term metal exposure, additions of Cu were used. Bacterial growth rates and respiration rates decreased in response to long-term metal contamination, while fungal growth rates were unaffected, without changes in CUEs. Bacterial biomass concentrations were independent of soil metal concentrations while fungal and total biomass decreased. Thus, turnover times for bacteria were slowed while fungal turnover times were accelerated by metal pollution. Bacterial growth was inhibited and fungal growth stimulated by experimental Cu additions, with bigger effect sizes in contaminated sites. We interpreted the low rates of growth but high biomass in collected soil samples to indicate that the fungal community included a large mycorrhizal fraction. Although Cu additions decreased the overall microbial OM-use (i.e., the sum of fungal and bacterial growth and total respiration), they also increased the CUE. In conclusion, fungal OM-use was less sensitive than bacterial to metal pollution and the CUE was unaffected. Microbial decomposer communities in contaminated soils were also able to maintain higher CUE when challenged with new metal additions. Our results imply that microbial communities align their trait compositions to environmental challenges, and that this can mitigate the reduction in microbial carbon-use efficiencies that often is expected to occur from environmental stress.

Optimization of extrinsic parameters for beneficiation of coal with the help of Cronobacter sp

ABSTRACT Beneficiation increases the calorific value of low-grade coal and extracts environmentally sensitive elements. Bacteria may be used as eco-friendly coal cleaning tool, but the treatment is influenced by several extrinsic and intrinsic factors. This study examined five extrinsic factors, namely particle size of coal, pulp density, bacterial biomass concentration, number of bacterial beads (immobilized bacterial cells) and the duration of treatment. For optimization, the test runs were designed using Taguchi L16 orthogonal array, determining optimal values through S/N ratio analysis and individual parameter contribution using ANOVA. The optimal conditions obtained for sub-bituminous coal beneficiation using Cronobacter sp. are 80–120 mesh particle size, 30% pulp density, 750 mg bacterial biomass/g coal, 25 bacterial beads, and six days of treatment resulting in 13.36% ash yield reduction. Particle size had the highest impact (69.4%), followed by treatment duration (13.1%), pulp density (6.3%), bacterial biomass (6.3%), and bacterial bead number (4.8%). A regression model attributed only 42% influence of these extrinsic factors on inorganic removal from coal. Therefore, further research on other factors, particularly intrinsic ones, in inorganic matter liberation is imperative. These findings can be used for designing experiments that optimize the extraction of cleaner fuel from various types of low-grade coal.

Properties of Degradable Polyhydroxyalkanoates Synthesized from New Waste Fish Oils (WFOs).

The synthesis of PHA was first investigated using WFOs obtained from smoked-sprat heads, substandard fresh sprats, and fresh mackerel heads and backbones. All the WFOs ensured the growth of the wild-type strain Cupriavidus necator B-10646 and the synthesis of PHA, regardless of the degree of lipid saturation (from 0.52 to 0.65) and the set and ratio of fatty acids (FA), which was represented by acids with chain lengths from C14 to C24. The bacterial biomass concentration and PHA synthesis were comparable (4.1-4.6 g/L and about 70%) when using WFO obtained from smoked-sprat heads and fresh mackerel, and it was twice as high as the bacterial biomass concentration from the fresh sprat waste. This depended on the type of WFO, the bacteria synthesized P(3HB) homopolymer or P(3HB-co-3HV-co-3HHx) copolymer, which had a lower degree of crystallinity (Cx 71%) and a lower molecular weight (Mn 134 kDa) compared to the P(3HB) (Mn 175-209 kDa and Cx 74-78%) at comparable temperatures (Tmelt and Tdegr of 158-168 °C and 261-284 °C, respectively). The new types of WFO, studied for the first time, are suitable as a carbon substrates for PHA synthesis. The WFOs obtained in the production of canned Baltic sprat and Baltic mackerel can be considered a promising and renewable substrate for PHA biosynthesis.

Biosynthesis and Properties of a P(3HB-co-3HV-co-4HV) Produced by Cupriavidus necator B-10646.

Synthesis of P(3HB-co-3HV-co-4HV) copolymers by the wild-type strain Cupriavidus necator B-10646 on fructose or sodium butyrate as the main C-substrate with the addition of γ-valerolactone as a precursor of 3HV and 4HV monomers was studied. Bacterial cells were cultivated in the modes that enabled production of a series of copolymers with molar fractions of 3HV (from 7.3 to 23.4 mol.%) and 4HV (from 1.9 to 4.7 mol.%) with bacterial biomass concentration (8.2 ± 0.2 g/L) and PHA content (80 ± 2%). Using HPLC, DTA, DSC, X-Ray, SEM, and AFM, the physicochemical properties of copolymers and films prepared from them have been investigated as dependent on proportions of monomers. Copolymers are characterized by a reduced degree of crystallinity (Cx 38–49%) molecular weight characteristics Mn (45–87 kDa), and Mw (201–248 kDa) compared with P(3HB). The properties of the films surface of various composition including the porosity and surface roughness were studied. Most of the samples showed a decrease in the average pore area and an increase in their number with a total increase in 3HV and 4HV monomers. The results allow scaling up the productive synthesis of P(3HB-co-3HV-co-4HV) copolymers using Cupriavidus necator B-10646.

Sugar Beet Molasses as a Potential C-Substrate for PHA Production by Cupriavidus necator.

To increase the availability and expand the raw material base, the production of polyhydroxyalkanoates (PHA) by the wild strain Cupriavidus necator B-10646 on hydrolysates of sugar beet molasses was studied. The hydrolysis of molasses was carried out using β-fructofuranosidase, which provides a high conversion of sucrose (88.9%) to hexoses. We showed the necessity to adjust the chemical composition of molasses hydrolysate to balance with the physiological needs of C. necator B-10646 and reduce excess sugars and nitrogen and eliminate phosphorus deficiency. The modes of cultivation of bacteria on diluted hydrolyzed molasses with the controlled feeding of phosphorus and glucose were implemented. Depending on the ratio of sugars introduced into the bacterial culture due to the molasses hydrolysate and glucose additions, the bacterial biomass concentration was obtained from 20–25 to 80–85 g/L with a polymer content up to 80%. The hydrolysates of molasses containing trace amounts of propionate and valerate were used to synthesize a P(3HB-co-3HV) copolymer with minor inclusions of 3-hydroxyvlaerate monomers. The introduction of precursors into the medium ensured the synthesis of copolymers with reduced values of the degree of crystallinity, containing, in addition to 3HB, monomers 3HB, 4HB, or 3HHx in an amount of 12–16 mol.%.

Deconvoluting algal and bacterial biomass concentrations in algal-bacterial suspensions

Algae and algal-bacterial consortia have many applications including biofuel production, as source of many beneficial products, and in wastewater treatment. With increasing interest in such systems, a suitable method to estimate the individual biomass concentrations of algae and bacteria in a mixed suspension is still not available. The objective of this study was to develop a method for estimating the algal and bacterial concentrations in suspensions containing both algae and bacteria. The method involved (1) determination of algal number concentration in the algal-bacterial suspension through manual algal cell counting, (2) conversion of the algal number concentration to algal mass concentration by applying a consolidated conversion factor, and (3) determination of bacterial mass concentration in the suspension by subtracting the algal mass concentration from the gravimetrically determined total biomass concentration in the suspension. Using the protocols developed in this study, algal biomass concentrations estimated in purely algal or artificially constituted algal-bacterial suspensions were comparable, both in terms of mean values and precision, to the corresponding algal biomass concentrations determined through direct gravimetric measurements. Estimations of algal and bacterial biomass concentration in suspensions with unknown algae and bacteria concentrations are also reported.

Defining manganese(II) removal processes in passive coal mine drainage treatment systems through laboratory incubation experiments

Oxic limestone beds are commonly used for the passive removal of Mn(II) from coal mine drainage (CMD). Aqueous Mn(II) is removed via oxidative precipitation of Mn(III/IV) oxides catalyzed by Mn(II)oxidizing microbes and Mn oxide (MnOx) surfaces. The relative importance of these two processes for Mn removal was examined in laboratory experiments conducted with sediments and CMD collected from eight Mn(II)-removal beds in Pennsylvania and Tennessee, USA. Sterile and non-sterile sediments were incubated in the presence/absence of air and presence/absence of fungicides to operationally define the relative contributions of Mn removal processes. Relatively fast rates of Mn removal were measured in four of the eight sediments where 63–99% of Mn removal was due to biological oxidation. In contrast, in the four sediments with slow rates of Mn(II) removal, 25–63% was due to biological oxidation. Laboratory rates of Mn(II) removal were correlated (R 2 = 0.62) to bacterial biomass concentration (measured

Linear Correlation between Online Capacitance and Offline Biomass Measurement up to High Cell Densities in Escherichia coli Fermentations in a Pilot-Scale Pressurized Bioreactor

To yield high concentrations of protein expressed by genetically modified Escherichia coli, it is important that the bacterial strains are cultivated to high cell density in industrial bioprocesses. Since the expressed target protein is mostly accumulated inside the E. coli cells, the cellular product formation can be directly correlated to the bacterial biomass concentration. The typical way to determine this concentration is to sample offline. Such manual sampling, however, wastes time and is not efficient for acquiring direct feedback to control a fedbatch fermentation. An E. coli K12-derived strain was cultivated to high cell density in a pressurized stirred bioreactor on a pilot scale, by detecting biomass concentration online using a capacitance probe. This E. coli strain was grown in pure minimal medium using two carbon sources (glucose and glycerol). By applying exponential feeding profiles corresponding to a constant specific growth rate, the E. coli culture grew under carbon-limited conditions to minimize overflow metabolites. A high linearity was found between capacitance and biomass concentration, whereby up to 85 g/L dry cell weight was measured. To validate the viability of the culture, the oxygen transfer rate (OTR) was determined online, yielding maximum values of 0.69 mol/l/h and 0.98 mol/l/h by using glucose and glycerol as carbon sources, respectively. Consequently, online monitoring of biomass using a capacitance probe provides direct and fast information about the viable E. coli biomass generated under aerobic fermentation conditions at elevated headspace pressures.

Effects of Cow Diet on the Microbial Community and Organic Matter and Nitrogen Content of Feces

Knowledge of the effects of cow diet on manure composition is required to improve nutrient use efficiency and to decrease emissions of N to the environment. Therefore, we performed an experiment with nonlactating cows to determine the consequences of changes in cow rations for the chemical characteristics and the traits of the microbial community in the feces. In this experiment, 16 cows were fed 8 diets, differing in crude protein, neutral detergent fiber, starch, and net energy content. These differences were achieved by changing dietary ingredients or roughage to concentrate ratio. After an adaptation period of 3 wk, fecal material was collected and analyzed. Observed results were compared with simulated values using a mechanistic model that provides insight into the mechanisms involved in the effect of dietary variation on fecal composition. Feces produced on a high-fiber, low-protein diet had a high C:N ratio (>16) and had lower concentrations of both organic and inorganic N than feces on a low-fiber, high-protein diet. Fecal bacterial biomass concentration was highest in high-protein, high-energy diets. The fraction of inorganic N in the feces was not significantly different between the different feces. Microbial biomass in the feces ranged from 1,200 to 8,000μg of C/g of dry matter (average: 3,700μg of C/g of dry matter). Bacterial diversity was similar for all fecal materials, but the different protein levels in the feeding regimens induced changes in the community structure present in the different feces. The simulated total N content (Ntotal) in the feces ranged from 1.0 to 1.5 times the observed concentrations, whereas the simulated C:Ntotal of the feces ranged from 0.7 to 0.9 times the observed C:Ntotal. However, bacterial biomass C was not predicted satisfactorily (simulated values being on average 3 times higher than observed), giving rise to further discussion on the definition of microbial C in feces. Based on these observations, it was concluded that diet composition affected fecal chemical composition and microbial biomass. These changes may affect the nutrient use and efficiency of the manure. Because the present experiment used a limited number of dry cows and extreme diet regimens, extrapolation of results to other dairy cow situations should be done with care.

Vegetation Removal Effects on Soil Quality in a Native Tallgrass Prairie Fragment in East-Central Arkansas

Severe fragmentation as a result of the introduction and expansion of mechanized agriculture has decimated the once dominant tallgrass prairie throughout much of the mid-western and mid-southern United States. In Arkansas, the Arkansas Natural Heritage Commission is charged with managing many of the remaining remnant tallgrass prairie fragments as Natural Areas. Though managed nearly annually by prescribed burning, a number of Natural Areas in Arkansas are hayed at least once a year. Since haying removes aboveground vegetation, many essential plant nutrients contained in that vegetation are also removed and are not returned to the same soil from which they were extracted. Therefore, the objective of this study was to evaluate the effects of vegetation removal (i.e., haying) on soil physical, chemical, and biological properties of a native tallgrass prairie fragment in east-central Arkansas. The study site was the Konecny Prairie Natural Area, which contains three areas of differing durations of vegetation removal by haying. Soil bulk density and bacterial biomass concentration in the top 10 cm were highest in the prairie area where vegetation removal by haying is still being conducted, while the prairie area where vegetation removal by haying ceased in 1998 had the highest soil organic matter, but lowest Ca and Mn contents. The effects of duration of vegetation removal by haying on native soil quality were variable and, for some soil properties, unexpected. Remnant prairie fragments can provide benchmark soil data for many properties to help ascertain the effects of land use change, particularly conversion to cultivated agriculture, and can provide target values for soil properties in ecosystem restoration efforts.

Bioremediation of a polycyclic aromatic hydrocarbon‐contaminated soil by using different aerobic batch bioreactor systems

The intrinsic depuration capability of a soil contaminated by polycyclic aromatic hydrocarbons (PAHs) originating from a contaminated industrial site was evaluated in this study by using different aerobic batch bioreactors: a slurry‐phase bioreactor, a blade‐agitated bioreactor, and a rotary vessel bioreactor. For each bioreactor, the disappearance of 14 target PAHs and of the total extractable organic matter was monitored. The three treatments exhibited rapid and extensive removal of the PAHs, which disappeared at different degradation rates according to their molecular weight and aromaticity degree. PAHs with two, three, and four aromatic rings were degraded in sequence, with average rates that generally decreased as the number of molecule rings increased. A slight increase in the bacterial biomass concentration and significant CO2 production were also observed during the time course of the treatments. Among the three treatments, the slurry‐phase system provides the most effective and fastest removal of the PAHs and the organic extractable matter. However, the semisolid‐phase systems exhibited PAH depletion, capabilities higher than those reported in the literature for soils with similar particle size distribution in solid‐phase conditions.

Changes in growth culture FDA activity under changing growth conditions

The FDA hydrolysis capacities and bacterial biomass concentrations (estimated by determination of ATP content) of growth cultures prepared from activated sludge and wastewater, were measured to find out whether the FDA activity would reflect bacterial biomass under different physiological states of the bacteria. The FDA activity/ATP ratio was calculated for different concentrations of autoclaved sludge. A faster decay rate of ATP relative to FDA hydrolysis activity was observed, thus causing changes in the ratio. Furthermore, comparison between values obtained from pure cultures and different soils revealed differences up to two orders of magnitude of the ratio. Based on these results it was concluded that the FDA activity should not be applied for measurements of viable biomass in environments in which different physiological conditions occur.

Sea Ice Microbial Communities: Distribution, Abundance, and Diversity of Ice Bacteria in McMurdo Sound, Antarctica, in 1980

An abundant and diverse bacterial community was found within brine channels of annual sea ice and at the ice-seawater interface in McMurdo Sound, Antarctica, in 1980. The mean bacterial standing crop was 1.4 x 10 cells m (9.8 mg of C m); bacterial concentrations as high as 1.02 x 10 cells m were observed in ice core melt water. Vertical profiles of ice cores 1.3 to 2.5 m long showed that 47% of the bacterial numbers and 93% of the bacterial biomass were located in the bottom 20 cm of sea ice. Ice bacterial biomass concentration was more than 10 times higher than bacterioplankton from the water column. Scanning electron micrographs showed a variety of morphologically distinct cell types, including coccoid, rod, fusiform, filamentous, and prosthecate forms; dividing cells were commonly observed. Approximately 70% of the ice bacteria were free-living, whereas 30% were attached to either living algal cells or detritus. Interactions between ice bacteria and microalgae were suggested by a positive correlation between bacterial numbers and chlorophyll a content of the ice. Scanning and transmission electron microscopy revealed a close physical association between epibacteria and a dominant ice alga of the genus Amphiprora. We propose that sea ice microbial communities are not only sources of primary production but also sources of secondary microbial production in polar ecosystems. Furthermore, we propose that a detrital food web may be associated with polar sea ice.