True Biomass Research Articles

Rapid shifts in catch composition in the artisanal Red Sea reef fisheries of Eritrea

Shifts in catch composition were registered in the Eritrean artisanal fisheries, which were launched into a renewed development after the end of the independence war in 1991. Our analysis of catch and effort data showed that total fishing effort as well as total annual catch increased more than two-fold from 1996 to 2002. Yet, overall CPUE remained unchanged upon the expansion of the fisheries, suggesting that the fisheries are still at an early stage of development. However, at lower taxonomic level, we found that the CPUE for emperors (Lethrinidae), snappers (Lutjanidae), and sharks (Elasmobranchii) decreased, while the CPUE for barracudas (Sphyraenidae), jacks (Carangidae), and tunas (Scombridae) increased. Thus, the species composition of the catches shifted toward a smaller proportion of high-value demersals (from ca. 70% in 1996 to ca. 30% in 2002), implying a change in the underlying fish community structure. Changes in CPUE could not be attributed to changes in spatial effort allocation, or to changes in gear or boats used, ruling out changes in fishing strategies as likely causes. Yet the decline in CPUE at low fishing effort does not necessarily reflect a proportional decline in fish abundance, and could possibly be caused by “hyperdepletion”. Nevertheless, the trends in CPUE are consistent with earlier findings that stocks of reef-associated demersal fishes are highly vulnerable to fishing and can decline even at the early stages of the fisheries. Therefore, the changes in CPUE could indeed represent true biomass changes, with potentially important ecological consequences. These effects could even become more severe if market conditions improve, leading to activation of latent fishing capacity, which was found to make up about 75% of the registered fleet.

The metabolic signature related to high plant growth rate in Arabidopsis thaliana

The decline of available fossil fuel reserves has triggered world-wide efforts to develop alternative energy sources based on plant biomass. Detailed knowledge of the relations of metabolism and biomass accumulation can be expected to yield powerful novel tools to accelerate and enhance energy plant breeding programs. We used metabolic profiling in the model Arabidopsis to study the relation between biomass and metabolic composition using a recombinant inbred line (RIL) population. A highly significant canonical correlation (0.73) was observed, revealing a close link between biomass and a specific combination of metabolites. Dividing the entire data set into training and test sets resulted in a median correlation between predicted and true biomass of 0.58. The demonstrated high predictive power of metabolic composition for biomass features this composite measure as an excellent biomarker and opens new opportunities to enhance plant breeding specifically in the context of renewable resources.

The effect of initial biomass in manipulative experiments on plants

Mass is often used as a measure of plant performance in manipulative experiments (Eviner et al. 2000; Shen & Harte 2000). Experimental manipulations may be very diverse: from addition of nutrients, to changing abiotic growth conditions, to removing or adding biotic components such as neighbours, herbivores, etc. But, in general, researchers try to clarify the effect of one factor by comparing the biomass of naturally growing plants (or transplants, or planted phytometers) under control and manipulated conditions. Experiments usually start with individuals that are young enough to avoid previous environmental effects, but mature enough to ensure survival and correct identification if several species are used. As a consequence, target individuals in both treatment and control have an initial mass prior to experiments. Established individuals are grown in different conditions and then harvested. The performance of target individuals is assessed by their final dry mass, and the initial value is often ignored in these analyses (Goldberg et al. 1999). However, ignoring the initial mass may conceal the treatment effects. Here we explore this problem, and show how ignoring initial biomass can cause systematic bias, particularly when experimental manipulation reduces plant performance compared with the control. Biomass accumulation during the experiment, or net increase in mass per unit time, can be described as:

Ecological implications of biomass and morphotype variations of bacterioplankton: an example in a coastal zone of the Northern Adriatic Sea (Mediterranean)

AbstractThis study had the objective of quantifying the variability in abundance, cell volume, morphology and C content of a natural bacterioplankton community in a coastal zone of the North Adriatic Sea during two periods (February and June) of two consequent years (1996 and 1997). We used epifluorescence microscopy with Acridine Orange staining procedures and a microphotographic technique. Low variability in bacterial abundance (range 0.3–3.1 × 105 cells ml−1) occurred between summer and winter periods. Conversely, the cell volume and the calculated carbon content changed greatly with warm and cold periods (ranges: 0.015–0.303 μm3 and 5.83–42.17 fg C cell−1, respectively). Elongated bacteria were dominant while coccoid cells prevailed only in February 1997. Biomass showed high variability (range 0.12–10.21 μg C l−1) whilst the abundance did not show noticeable differences among the sampling periods. As a consequence, quantification of bacterial biomass based solely on cell abundance must be considered with caution because the true biomass could depend on variability in cell volumes and morphotypes.

English

Data collected during high-cell-density cultivation of Saccharomyces cerevisiae DSM 2155 on glucose in a simulated five-phase feeding strategy of fed-batch process, executed on the Universal BIoprocess CONtrol (UBICON) system using 150L bioreactor over a period of 24h have been analysed. The consistency of the data set was checked using both the available electron and carbon balances. Estimates of the true energetic yields and cell maintenance requirements were obtained through the application of a multivariate statistical procedure known as covariate adjustment technique. A low value of maintenance coefficient, me = 0.004h -1 , and a high average value of the true biomass energetic yield, max = 0.745, were obtained for the bioreactor system, which showed that the organism was in no danger of ethanol produced during this cultivation. A simple model for estimating the distribution of substrate consumed between the fermentative and the respiratory pathways in the oxido-reductive process was developed based on the respiratory quotient (RQ) values. The fraction of substrate consumed for respiratory metabolic activities (qsresp/qs) was virtually 1.0 for the first three phases of the feeding strategy, which accounted for the first sixteen hours of the 24h operation. This was an indication that ethanol formation was avoided during this period.

Growth kinetics of the filamentous microorganism Sphaerotilus natans in a model system of a food industry wastewater

Bulking by Sphaerotilus natans has been attributed to several factors such as low dissolved oxygen in the aeration basin, wastes with high C:N ratios and phosphorus limitation; however, the occurrence of bulking has been reported in fruit, vegetable, meat and poultry wastewaters in which the ratio C:N is variable. Growth of S. natans was analyzed in a model system of a food industry wastewater (potato processing waste) that was characterized by HPLC determining that citric acid was the most important identified component. The effect of several carbon sources on S. natans growth was also studied; different C:N ratios were tested in a continuous culture system (chemostat). This strain grew in a mineral medium with citric acid as a sole carbon source, in spite of the contradictory results found in literature. Chemostat studies showed that the medium was carbon-limited when C:N ratios <19 mgCOD (mgN-NH 3) −1. Monod kinetic growth coefficients, determined for this strain in chemostat were: maximum specific growth rate, μ max=0.301 h −1; Monod constant, K S=4.6 mgCOD l −1; true biomass growth yield, Y T X/S=0.490 mgVSS (mgCOD) −1; endogenous decay rate, k d=0.011 h −1 and maintenance coefficient, m S=0.022 mgCOD (mgVSS) −1 h −1. The obtained parameters were compared with literature data and the effect of glucose and citric acid as carbon sources was discussed; these parameters are useful in modeling the growth of S. natans in potato processing wastewaters (or in other effluents under carbon-limiting conditions) especially when citrate is the main component and can be used to control filamentous bulking by metabolic or kinetic selection.

Stoichiometric analysis ofKluyveromyces fragilis growth on lactose

This paper describes results of the application of simple metabolic model principles to aerobic growth of Kluyveromyces fragilis during the utilisation of a semi-synthetic medium simulating dairy waste (whey). The theoretical yield coefficients (maximum, true and real) of biomass on lactose and oxygen, available electrons and ATP were determined and compared with experimental data. The experimental runs were performed in a B Brown fermenter (15 dm3 of operating capacity). The yeast K fragilis was cultured in semi-synthetic medium containing lactose (40 g dm−3) as a main carbon and energy source and ammonia salts as a main nitrogen source (C/N = 8.74). The yeast growth is closely related to the concentration of oxygen in the media. The experimental yields of biomass on lactose and oxygen reached 94% and 88% of real maximum theoretical values, respectively. Calculated true biomass yield coefficients were closely correlated with the values resulting from the balance analysis of stoichiometric equations. The specific maintenance requirement (mATP) was 14.7 mmole ATP(g DM h)-1. Determination of the elemental composition of the biomass during the course of fermentation resulted in observations of the cellular C/N ratio changes. The conversion of lactose carbon to biomass and CO2 was 74.3%–81.2%. The recovery of ATP reached 79%, and the recovery of oxygen 96.2%. © 2000 Society of Chemical Industry

Effect of chromium(VI) on the biomass yield of activated sludge

Effect of 1–25 mg/l of influent Cr(VI) concentrations on true biomass yield ( Y t) and decay coefficient ( k d) of activated sludge units was investigated in this study. To this purpose, completely mixed, once-through laboratory scale activated sludge units with acclimated cultures were operated. After obtaining dilute-out curves for each Cr(VI) concentration, the values of Y t and k d were determined. The results revealed that presence of Cr(VI) caused stimulatory effects on biomass yield and maintenance up to the Cr(VI) concentration of 25 mg/l. Lower Cr(VI) concentrations exerted higher stimulation of the system. Extended oxidation due to the presence of Cr(VI) and/or increased synthesis of cellular material due to the stimulatory effects of Cr(VI) were thought to be the mechanisms of the observed stimulation.

Optimisation of the design parameters in an activated sludge system for the wastewater treatment of a potato processing plant

Aerated biological reactors at a laboratory scale, fed continuously with a model wastewater system, were used to obtain design parameters of an activated sludge process for the wastewater treatment of a potato processing plant. Experiments were performed using different dilution rates ( D) ranging between 0.01 and 0.13 h −1 to determine parameters such as: maximum specific microbial growth rate ( μ max), saturation constant ( K s), coefficient of microbial decay ( k d) and true biomass yield ( Y X/S). Design parameters were calculated from the mass balances of substrate consumption and biomass production under steady state, considering a Monod-type equation to represent the effect of substrate concentration on biomass production rate. The values of Y X/S and k d were obtained from the linear plot of q S (specific rate of substrate consumption) vs. D. Experimental data regression led to Y X/S=0.45 gVSS/g COD and k d=0.024 h −1. By non-linear regression of q S vs. substrate concentration ( S S) data the following values were obtained μ max=0.09 h −1 and K s=0.006 g/l. Critical dilution rate was also calculated; it corresponds to the D value for which the cells of a reactor operating under such conditions are destroyed or are eliminated from the system at the same rate than they are produced.

Intracellular storage compounds, oxygen uptake rates and biomass yield with readily and slowly degradable substrates

An experimental study was undertaken to quantify the effects of intracellular storage polymers on the Oxygen Uptake Rate (OUR) profile and biomass yield coefficients for readily and slowly degradable substrates using a sludge from anaerobic-aerobic Sequencing Batch Reactor (SBR). Glucose and acetate were chosen as readily biodegradable substrates and soluble starch served as a model polymeric slowly degradable substrate. In case of acetate as substrate, PHA was the major storage polymer while polysaccharide acted as the main storage compound in case of glucose and starch. The accumulation of storage compounds even in the case of starch suggests that storage may be an integral part of the metabolic process for the sludge having storage capabilities. The maximum storage amounted to about 45%, 68% and 36% of total acetate, glucose and starch COD removed from bulk respectively. A new approach to calculate the true biomass yield coefficients based on exogenous OUR and considering intracellular storage is proposed. The relative independence of the calculated yield values to the amount of storage makes them suitable for application in growth kinetics. The calculated yield coefficients based on the proposed approach worked out to be 0.24–0.28, 0.58–0.50 and 0.64 for acetate, glucose and starch respectively and were significantly lower than the yield coefficients calculated based on conventional approach of not accounting storage. Further, the average degradation rate of intracellular glycogen were estimated to be 15 mg carbohydrate COD/g. MLSS. hr. with an average biomass yield of 0.45 mg biomass COD/mg carbohydrate COD.

Resource‐based models of competitive Interactions. I. Intraspecific Competition In Ratibida columnifera (Asteraceae)

We constructed and tested a series of regression models of intraspecific competition in Ratibida columnifera (Asteraceae), based on the growth and water use of individual plants. Models were constructed from a set of plants ("model") grown without competition under three watering regimes. Each model was then tested on another set of plants ("test") grown, singly or in pairs, under two watering regimes, one of them different than those of the "model" plants. Both sets of plants were grown simultaneously. Models that used only estimates of plant dry mass (ISON [interval by interval size only], and SON [size only]) were outperformed (i.e., the difference between predicted values of final dry mass and their true values were larger on average) by models that incorporated direct measures of water uptake and usage (ISAW [interval by interval size and water], WON [water only], SAW [size and water]). Harvest biomass predictions given by these three last models deviated from values of true biomass by an average of only 6.1%.

Intracellular storage compounds, oxygen uptake rates and biomass yield with readily and slowly degradable substrates

An experimental study was undertaken to quantify the effects of intracellular storage polymers on the Oxygen Uptake Rate (OUR) profile and biomass yield coefficients for readily and slowly degradable substrates using a sludge from anaerobic-aerobic Sequencing Batch Reactor (SBR). Glucose and acetate were chosen as readily biodegradable substrates and soluble starch served as a model polymeric slowly degradable substrate. In case of acetate as substrate, PHA was the major storage polymer while polysaccharide acted as the main storage compound in case of glucose and starch. The accumulation of storage compounds even in the case of starch suggests that storage may be an integral part of the metabolic process for the sludge having storage capabilities. The maximum storage amounted to about 45%, 68% and 36% of total acetate, glucose and starch COD removed from bulk respectively. A new approach to calculate the true biomass yield coefficients based on exogenous OUR and considering intracellular storage is proposed. The relative independence of the calculated yield values to the amount of storage makes them suitable for application in growth kinetics. The calculated yield coefficients based on the proposed approach worked out to be 0.240.28, 0.58-0.50 and 0.64 for acetate, glucose and starch respectively and were significantly lower than the yield coefficients calculated based on conventional approach of not accounting storage. Further, the average degradation rate of intracellular glycogen were estimated to be 15 mg carbohydrate COD/g. MLSS. hr. with an average biomass yield of 0.45 mg biomass COD/mg carbohydrate COD.

Biomass estimation of orange roughy: a summary and evaluation of techniques for measuring stock size of a deep‐water fish species in New Zealand

A number of techniques have been employed to measure biomass of orange roughy in New Zealand. Time series of stratified random trawl surveys in a number of areas over periods of 5–10 years have given relative abundance indices, which have been used in stock reduction analyses to estimate true biomass. This has given confident results for the Chatham Rise stock, and surveys have also shown strong trends in other regions. Acoustic surveys have been carried out on three grounds. They can give relative indices of orange roughy abundance in areas of fiat or medium sloping bottom, and have the potential for estimation of absolute biomass from a single survey. Egg production surveys have been employed on two grounds on the east coast of the North Island, where conditions of tight spawning aggregations and steep bottom topography have limited the success of other methods. Both daily fecundity reduction and annual egg production methods have been used. These have given estimates of true biomass from one‐off surveys, although results are imprecise. Both unstandardized and standardized analyses of commercial catch‐per‐unit‐effort data have given relative indices of abundance, which have formed an important part of stock assessment for several fisheries. No single technique used to measure the size of orange roughy stocks has proven ideal or appropriate in all New Zealand situations. All have advantages and disadvantages, depending on the characteristics of the fishing area and fish behaviour. For two areas, a combination of methods have been applied, which has given more confident results than those from a single technique.

Effect of nickel(II) on the biomass yield of the activated sludge

Biomass yield of microorganisms is important in applied microbiology since it is the ultimate factor determining the amount of product produced regardless of whether product is growth-linked or not. In the case of environmental microbiology the opposite is true and minimizing the biomass produced, or the sludge in the relevant jargon, often is the prime goal. In this paper, a unique means of manipulating the microbial biomass yield of a heterogeneous culture to fulfil either of the two goals is presented. 5.0 mgl−1 Ni(II) in the feed composition to a completely mixed, once- through, activated sludge was found to induce the observed biomass yield of the microbial culture developed from sewage. As compared with the base-line study without Ni(II), where the reactor received synthetic wastewater only, true biomass yield was found to have increased along with the increased decay constant with the net effect of lowering observed biomass yield drastically at lower dilution rates and increasing it over that observed in the base-line study at higher dilution rates. At 10.0 mgl−1 influent Ni(II) concentration the culture conditions almost reverted back to the base- line study and at 25 mgl−1 Ni(II) concentration a truly steady-state condition could not be attained.

Determination of yield and maintenance coefficients in citric acid production by Aspergillus niger

One method for economic planning and management of production processes is a balance of substrate mass and energy it contains. Theoretical assumptions and practical applications of mass and energy balances in the process of citric acid production by Aspergillus niger are discussed in the study. In the calculation of biomass and product yields as well as the maintenance coefficients mechanistic values such as true biomass and citric acid yields Y max ATP,X(P) on ATP and specific ATP consumption m ATP due to maintenance processes were used. A set of limitations imposed on theoretical and true yield coefficients in the linear growth equation is also presented. The experimental measurements were performed in an air-lift bioreactor of 220 dm 3 operating capacity, with external circulation loop. The sole carbon source for the cultivation of A. niger was sucrose at an initial concentration of 100 g l −1. The experimentally obtained yield coefficients relative to cell growth and citric acid production have reached 96% and 83% respectively of real maximum theoretical values. Calculated true biomass and citric acid yield coefficients were closely correlated with the values from the balance analysis of stoichiometric equations. Calculated value of specific maintenance requirements m ATP was 0.015 mol ATP [mol C(dry mass)] −1 h −1.

Effect of nickel(II) on the biomass yield of the activated sludge

Biomass yield of microorganisms is important in applied microbiology since it is the ultimate factor determining the amount of product produced regardless of whether product is growth-linked or not. In the case of environmental microbiology the opposite is true and minimizing the biomass produced, or the sludge in the relevant jargon, often is the prime goal. In this paper, a unique means of manipulating the microbial biomass yield of a heterogeneous culture to fulfil either of the two goals is presented. 5.0 mgl−1 Ni(II) in the feed composition to a completely mixed, once- through, activated sludge was found to induce the observed biomass yield of the microbial culture developed from sewage. As compared with the base-line study without Ni(II), where the reactor received synthetic wastewater only, true biomass yield was found to have increased along with the increased decay constant with the net effect of lowering observed biomass yield drastically at lower dilution rates and increasing it over that observed in the base-line study at higher dilution rates. At 10.0 mgl−1 influent Ni(II) concentration the culture conditions almost reverted back to the base- line study and at 25 mgl−1 Ni(II) concentration a truly steady-state condition could not be attained.

Estimation of the energetic parameters associated with the aerobic degradation of quinoline by Comamonas acidovorans in continuous culture

AbstractAn estimation of the true growth yields and maintenance coefficients for Comamonas acidovorans DSM 6426 under continuous cultivation on quinoline has been performed. The data were checked for consistency using available electron, carbon and nitrogen balances. The true biomass energetic yields, ηmax, and energetic maintenance coefficients, me, were estimated using two models based on control of growth rate and control of substrate uptake rate, respectively. The estimations were converted to the various familiar true growth yield and maintenance units such as substrate‐based (Y, mS/X), oxygen‐based (Y, m) and carbon dioxide‐based (Y, m) units. For the complete mineralization of quinoline by C. acidovorans, values of ηmax = 0.371 and me = 0·0426 h−1 were obtained.

Estimation of true biomass energetic yield and maintenance coefficient with errors in the variables

AbstractSimple regression analysis is based on the least square of residual errors. To use this method, an independent variable which is observable without error is assumed to exist. For most analyses, the assumption is normally made without realising the implications. The present study demonstrates how parameters may be estimated with the assumption of error in all measurements. Data sets involving batch/fed‐batch cultivation of Candida utilis were analysed using a statistical approach with error in variables for the estimation of true biomass energetic yield and maintenance coefficient. This approach requires replicated measurements. For linear systems, such as in chemical/biochemical processes, replicated measurements are sometimes possible or there are physical/physiological reasons to group the observations into clusters. When clusters of replicated measurements are not available, the cluster analysis technique may be used to identify groups of near‐replicated data points. The procedure yielded similar results to those obtained by the ordinary least squares procedure for consistent data. However, for data of poor quality (especially data with large errors in the independent variable), the disparity between the two procedures was more significant.

Analysis of the respiro-fermentative growth of Saccharomyces cerevisiae on glucose in a fed-batch fermentation strategy for accurate parameter estimation

Analysis of the respiro-fermentive growth of a strain of Saccharomyces cerevisiae, DSM 2155 on glucose, in a simulated 5-phase feeding strategy of fedbatch cultures executed on the Universal BIoprocess CONtrol (UBICON) system, was carried out. There was a good agreement between the estimated and the simulated values of specific growth rates. In this study, which was designed to span 0.20–0.23 h−1 growth rates before returning to lower growth rates, the critical dilution rate at which the switch between purely oxidative and respiro-fermentative growth takes was not observed. The biomass yield, specific substrate uptake and O2 consumption rates as well as the consistency of the data using both carbon and available electron balances were examined. A high average value of true biomass energetic yield, ηmax = 0.707, and a low value of maintenance coefficient, me = 0.0114 h−1, were obtained indicating that the organism was in no danger from the ethanol produced as a high-density fermentation with a yeast concentration above 54 g 1−1 was possible within a period of 24 h. The yeast produced also had good dough-leavening characteristics. Thus it is possible to operate a yeast plant without resorting to using respiratory quotient, which may be problematic, as the controlling parameter.

Energetics of Pseudomonas cepacia G4 growth in a chemostat with phenol limitation

AbstractAnalysis of the growth of Pseudomonas cepacia G4 on phenol in continuous culture has been carried out. The data were checked for consistency using both available electron and carbon balances. Coupled with the covariate adjustment estimation technique, the best estimates for true biomass energetic yield, ηmax and maintenance, me, were obtained when the carbon dioxide measurements were excluded. However, upon making corrections to the gas measurements, the best estimates were the maximum likelihood estimates (MLE) based on the complete data. The method therefore allows discrimination to be made between data. Also, similar estimates were obtained using Pirt's model based on the Monod approach and a modified form based on substrate uptake rate being the limiting factor. For the aerobic growth of P. cepacia G4 on phenol, ηmax = 0·417 and me = 0·0513 h−1 were obtained when the CO2 data were excluded. When corrections were made to the gas measurements to take into account the dissolved CO2 and the effect of operating temperature, ηmax = 0·432 and me = 0·0684 h−1 were obtained. From the 95% confidence intervals, a maximum of about 38–47·5% of the energy contained in phenol is incorporated into the biomass while the balance (52·5–62%) is evolved as heat with only a little energy needed for the maintenance of the organism.