Cylindroconical Tanks Research Articles

Batch-to batch variation in nutrient digestibility of black soldier fly larvae meals in rainbow trout

Abstract The aim of this study was to evaluate the apparent digestibility coefficients (ADCs) of four batches of black soldier fly (BSF) meal, named BSF1, BSF2, BSF3 and BSF3, produced by the same company over one year, in rainbow trout (Oncorhynchus mykiss). To assess nutrients and amino acids ADCs, each insect meal was mixed with a high-quality reference diet in a 30:70 ratio on as is basis, including celite as inert marker, and pelleted. The reference diet was also used as control. The ADCs were calculated based on the data collected and determined during an in vivo experiment. A total of 240 fish were randomly divided into 250-L cylindroconical tanks supplied in flow-through open and Choubert systems (3 replicates/treatment). Data were analysed by One-Way ANOVA (SPSS V20.0.0.; ). Globally, the four BSF meals showed a high ADC value, between 82.6 and 100%. No statistically significant differences were observed in the ADCs of dry matter, crude protein, ether extract and gross energy, while some differences were observed in the amino acid profile (). Generally, fish fed on BSF1 displayed reduced digestibility for histidine, isoleucine, leucine, valine, alanine, proline, and glycine compared to BSF2 and BSF4 meals (), while the BSF3 group showed intermediate results (). Despite the good digestibility of nutrients for all the insect mealsthe implementation of standardized production is important to have a standardize BSF meal capable of meeting market demands.

The Use of Acartia tonsa Nauplii during the First Days of Feeding on the Ontogeny of the Digestive System of Greater Amberjack (Seriola dumerili Risso, 1810)

The effect of feeding greater amberjack with copepod nauplii (Acartia tonsa) on the ontogeny of the digestive system was observed until 40 days after hatching (DAH). Copepods are part of the diet of fish larvae in nature, and they are rich in highly unsaturated fatty acids and free amino acids that enhance the digestive capacity of the fish. In a marine hatchery, four cylindroconical tanks of 2,700 L were stocked with about 150 × 103 greater amberjack larvae (Seriola dumerili) in each. The larvae were initially fed from 3 to 17 DAH in two tanks with copepod nauplii and rotifers (Brachionus sp.; Copepods group), while in the other two tanks, they were fed only with rotifers (Control group) during the same period. All the tanks were fed with rotifers (3–27 DAH), Artemia nauplii (12–22 DAH), enriched Artemia metanauplii (20–30 DAH), and formulated diet (25–40 DAH). Fish samples were taken regularly (every 2 or 4 days) for histological analysis and every day for the measurement of total length (TL). The TL was 3.7, 4.5 ± 0.1, 6.1, 11, 17.3 ± 0.1 and 20.3 ± 2.3 mm at 4, 10, 16, 22, 30, and 40 DAH, respectively. Copepod-fed fish showed higher TL in the last 2 days of the trial (p <0.05), while mortality rates were lower in the beginning of the trial 10–17 DAH, (p <0.05). In addition, copepods-fed fish had less skeletal deformities (p <0.05). Pyloric caeca appeared earlier in the Copepods group compared with the Control, while the length and surface of the villi, the abundance of goblet cells/100 μm of intestine length, and the area covered with lipid vacuoles in the liver were significantly higher in the Copepods group (p <0.05). We can conclude that the use of copepods in the diet of the greater amberjack larvae can improve the ontogeny of the digestive system.

The effect of copepod Acartia tonsa during the first days of larval rearing in skeleton ontogeny and skeletal deformities in greater amberjack (Seriola dumeliri Risso, 1810)

The effect of feeding greater amberjack (Seriola dumerili) with copepod nauplii (Acartia tonsa) on osteological development was observed until 35 days after hatching (DAH). The skeletal deformities were observed at the end of the trial. Copepods are the natural food of marine fish larvae, and they are rich in highly unsaturated fatty acids and free amino acids. In a commercial marine fish hatchery in Greece (Galaxidi Marine Farm S.A.), four 2700 l cylindroconical tanks were stocked with amberjack yolk-sac larvae at a density of about 55 larvae/l. The larvae were initially fed from 3 to17 DAH in two tanks with copepod nauplii and rotifers (Brachionus sp.) (Copepods group), while in the other two tanks, only with rotifers (Control group). After 12 DAH, all the tanks were also fed with rotifers (3–27 DAH), Artemia nauplii (12–22 DAH), enriched Artemia metanauplii (20–30 DAH), and formulated diet (25–30 DAH). Fish samples were taken every three days, fixed in phosphate-buffered 5% formalin (pH = 7.2). Bone and cartilage were stained with alizarin red and alcian blue, respectively. Specific meristic characters were chosen to compare the first appearance and the completion of the formation of a structure as well as the completion of the calcification between the two rearing protocols (Copepods - Control), correlated with total length data. These meristic characters included replacement and membranous bones from the vertebral column and all the fins. The ontogeny of the meristic characters was observed earlier in fish larvae from the Copepods group compared with the Control, and for most of the meristic characters, these differences were significant (p < 0.05). TL50 data analysis was performed, and the results were similar. At the end of the trial, 35 DAH sixty fish from each tank were sampled for the analysis of skeletal deformities. A higher number and more significant deformities were observed in the Control group compared with the Copepods group (p < 0.05). In conclusion, the use of copepod nauplii during the first feeding period of greater amberjack had a positive effect on the osteological development and skeletal deformities of the larvae.

Polygenic Analysis of Tolerance to Carbon Dioxide Inhibition of Isoamyl Acetate "Banana" Flavor Production in Yeast Reveals MDS3 as Major Causative Gene.

ABSTRACTThe introduction in modern breweries of tall cylindroconical fermentors, replacing the traditional open fermentation vats, unexpectedly revealed strong inhibition of flavor production by the high CO2 pressure in the fermentors. We have screened our collection of Saccharomyces cerevisiae strains for strains displaying elevated tolerance to inhibition of flavor production by +0.65 bar CO2, using a laboratory scale CO2 pressurized fermentation system. We focused on the production of isoamyl acetate, a highly desirable flavor compound conferring fruity banana flavor in beer and other alcoholic beverages, from its precursor isoamyl alcohol (IAAc/Alc ratio). We selected the most tolerant Saccharomyces cerevisiae strain, saké yeast Kyokai no. 1, isolated a stable haploid segregant seg63 with the same high IAAc/Alc ratio under CO2 pressure, crossed seg63 with the unrelated inferior strain ER7A and phenotyped 185 haploid segregants, of which 28 displaying a high IAAc/Alc ratio were pooled. Mapping of Quantitative Trait Loci (QTLs) by whole-genome sequence analysis based on SNP variant frequency revealed two QTLs. In the major QTL, reciprocal hemizygosity analysis identified MDS3 as the causative mutant gene, a putative member of the TOR signaling pathway. The MDS3Seg.63 allele was dominant and contained a single causative point mutation, T2171C, resulting in the F274S substitution. Introduction of MDS3Seg.63 in an industrial tetraploid lager yeast with CRISPR/Cas9 enhanced isoamyl acetate production by 145% under CO2 pressure. This work shows the strong potential of polygenic analysis and targeted genetic modification for creation of cisgenic industrial brewer's yeast strains with specifically improved traits.IMPORTANCE The upscaling of fermentation to very tall cylindroconical tanks is known to negatively impact beer flavor. Most notably, the increased CO2 pressure in such tanks compromises production by the yeast of the desirable fruity “banana” flavor (isoamyl acetate). The cause of the CO2 inhibition of yeast flavor production has always remained enigmatic. Our work has brought the first insight into its molecular-genetic basis and provides a specific gene tool for yeast strain improvement. We first identified a yeast strain with superior tolerance to CO2 inhibition of flavor production, and applied polygenic analysis to identify the responsible gene. We narrowed down the causative element to a single nucleotide difference, MDS3T2171C, and showed that it can be engineered into brewing yeast to obtain strains with superior flavor production in high CO2 pressure conditions, apparently without affecting other traits relevant for beer brewing. Alternatively, such a strain could be obtained through marker-assisted breeding.

Avrupa Istakozu (Hommarus gammarus) Larvalarının Düşük Yoğunluk Koşulları Altında Pseudo-Yeşil Su ve Temiz Suda Büyümesi ve Hayatta Kalması

The European lobster, Hommarus gammarus, is a commercially important species in Europe. Despite successful stock enhancement programs during the last two decades, culture methods of H. gammarus are still in progress. In this study, the effects of pseudo-green water technique and clear water technique with lower stocking densities on the growth and survival of H. gammarus larvae during stages I-IV were investigated. All larvae were reared in 800 L cylindro-conical tanks with a stocking density of 1.25 larvae/L at a temperature of 17.1±1 oC and a salinity of 32±1 ppt. Lobster larvae were fed with enriched Artemia at a density of 3-5 naupli/ml for a period of 10 (09:30 am- 19:30 pm) hours. Daily additions of concentrated algae increased turbidity and reduced visibility in tanks compared to clear water conditions. Results showed that growth of lobster larvae were not significantly different among treatments during planktonic stages I-IV (p&amp;gt;0.05). Overall mean survival rate was only 3% with no significant differences between treatments. Increased turbidity and lower stocking density did not improve survival rates. Further studies are required to develop methods that will promote higher survival rates during the pelagic stages of lobster larvae.

Simultaneous Optimization of Acetaldehyde and DMS Concentrations for Better Sensory Quality of Beer Fermented on an Industrial Scale

The levels of selected volatile components that affected the sensory properties of a lager beer were optimized under high-gravity brewing conditions (15.5 °P) in an industrial plant. The influence of different pitching rates (6–10 million cells/mL), aeration levels (8–12 mg/L), times (4.5–13.5 h) of filling CCTs (cylindroconical tanks, 3850 hl), and fermentation temperatures (8.5–11.5 °C) on the contents of acetaldehyde, diacetyl, acetone, 2,3-pentanedion, dimethyl sulfide (DMS), and on the sensory properties of beer were investigated. Response surface methodology (RSM, Box–Behnken design) was used to research the possibilities for optimizing the concentration of selected volatile components and sensory properties of bottom-fermented lager beers. Statistical analyses of the results showed that the experimental factors had a significant influence (R-squared for the original model with no significant lack-of-fit) on some of the volatile components. Based on the Multiple Response Optimization analysis, the values of independent factors that ensured the highest beer sensory quality were the following: a pitching rate of 10 million cells per mL; a fermentation temperature of 11.5 °C; an aeration level of 12 mg/L; and a CCT filling time of 4.5 h. These results proved that RSM modelling can be successfully applied to optimize fermentation and lagering processes in an industrial plant to manufacture lagers of enhanced sensory quality.

PRODUCTIVITY OF ROTIFER Brachionus plicatilis CULTURED UNDER BATCH SYSTEM BY USING SUGAR BEET MOLASSES AS A SUBSTITUTE MEDIUM

This study deals with the determination of availability of sugar beet molasses as a nutritional enrichment factor for rotifer cultures. A series of experiments under varying conditions such as ratio of sugar beet molasses in the nutrient complex were carried out in order to determine the effectiveness of sugar beet molasses as a carbohydrate and mineral source for the purpose of aquacultural operations. The culture water of Brachionus plicatilis with the salinity of 38% was treated through mechanical filtration and UV sterilization. 1 T cylindro-conical tanks are utilized for rotifer culture. Parameters of culture water were stabilized at values as following; Oxygen concentration:5 to 10 ppm, temperature: 27 0 C and pH:6.8 to 7.4. Rotifers were counted by using Sedgewick Rafter Cell on a daily basis in order to determine increase of number of individuals. The study was conducted as 3 different trial groups, each consisting three separate tanks, so triplicate determinations were obtained. For the Group I, 10% molasses by weight of Culture Selco Plus (200 gr Selco Plus+20 gr molasses per tank) was added 6 times a day with 4 hours’ intervals. For the Group II, 20% molasses by weight of Culture Selco Plus (200gr Selco Plus+40gr molasses per tank) was added and lastly for the control group, Group III, no molasses has been added and 200 gr Culture Selco Plus was only added per tank. The addition of molasses to nutritive complex has a decreasing effect on the number of rotifer and increasing effect on the number of ciliate. From the study, it is clear that sugar beet molasses should not be used as an additional nutritional factor for rotifer cultures due to its decreasing effect on the number rotifers and stimulating effect on the ciliate booming. Addition of 10% and 20% molasses resulted in 31.4% and 23.3% decrease in number of rotifers at the time of T3, respectively. On the other hand, it was observed that addition of molasses in the nutritive complex has not affected on the percentage of rotifers bearing eggs.

Apparent nutrient and fatty acid digestibilities of microbial raw materials for rainbow trout (Oncorhynchus mykiss) with comparison to conventional ingredients

Determination of apparent digestibility coefficients (ADC) of ingredients has a central importance in formulation of aquaculture diets. Heterotrophic and phototrophic grown microalgae are considered as one of the best eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) as well as protein alternatives for fish oil and fish meal (FM) to sustain further growth in aquaculture production. This study aimed to determine nutrient and fatty acid ADCs of microbial materials including Nannochloropsis oceanica, Phaeodactylum tricornutum and two thraustochytrid strains (T29 and T66) with comparison to commonly used ingredients such as two batches of FMs, poultry-by product meal (PBM), soybean meal (SBM), corn gluten meal (CGM), wheat gluten meal (WGM) and whole wheat flour (WF) in rainbow trout, Oncorhynchus mykiss. Each ingredient was tested using Cr2O3 as an indigestible marker in triplicated cylindro-conical tanks for 2 weeks. Protein ADCs of microbial ingredients ranged between 77.6% in T66 and 84.4% in P. tricornutum and were close to those of FMs and PBM. N. oceanica had generally significantly lower lipid and fatty acid ADCs than those of P. tricornutum, thraustochytrids and the conventional feed ingredients probably due to their thick cell walls. Between the thraustochytrids strains, the T66 appeared to have slightly lower lipid, energy, organic matter, saturated, monounsaturated, long chain n-6 and long chain n-3 fatty acid ADCs than T29. P. tricornutum showed comparable nutrient ADC values to the two FMs used in the study. The results suggest that even if the microbial ingredients were used at 30% in reference diet without exposition to a pretreatment process, they can be utilized at acceptable rates by rainbow trout.

Effect of yeast harvest moment on a brewing process in beer produced on an industrial scale

The aim of this study was to determine the effect of yeast harvest timing on the process performance, total yeast count and the content of volatile components in beer. The experiments were performed on an industrial scale with fermentation and maturation conducted in three fermentation tanks with a capacity of 3800 hl (cylindro-conical tanks – CCT). All processes were carried out using the same technological conditions. The worts were aerated with sterile air and yeast after the second fermentation (third generation) was added. The duration of the maturation phase and the processes of the yeast harvest were conducted at different times (1&lt;sup&gt;st&lt;/sup&gt;, 4&lt;sup&gt;th&lt;/sup&gt; and 6&lt;sup&gt;th&lt;/sup&gt; day) after finishing the primary fermentation process. During fermentation and maturation, changes in the contents of the extract, yeast, and volatile components were investigated. These experiments showed that the use of different times during yeast harvest had a significant impact on the course of fermentation and maturation and impact on the total yeast count during the maturation process and on the amount of volatile components in beer. With a delay in the start of yeast cropping, the content of acetaldehyde and vicinal diketones decreased and the content of esters increased. The timing of the yeast crop significantly influenced the final beer quality.

Spray-dried plasma promotes growth, modulates the activity of antioxidant defenses, and enhances the immune status of gilthead sea bream (Sparus aurata) fingerlings.

Terrestrial animal byproduct meals, including nonruminant blood meal and blood products, represent the largest and largely untapped safe source of animal protein available within the international market for the aquafeed industry. Spray-dried blood and spray-dried plasma (SDP) proteins have long been recognized as high-quality feed ingredients for farmed animals. In this study, we evaluated the inclusion of SDP from porcine blood (SDPP) in growing diets for gilthead sea bream. Three isonitrogenous (CP = 51.2%) and isolipidic (fat = 12.4%) diets manufactured by cold extrusion (0.8 to 1.5 mm pellet size) were prepared by substituting high-quality fish meal with 0, 3, and 6% SDPP. The diets were tested for a period of 60 d at 22°C with 4 replicates each (400-L cylindroconical tanks, 150 fish per tank, and initial density = 0.5 kg/m(3)). The SDPP inclusion in diets for gilthead sea bream fingerlings were evaluated in terms of growth performance, feed utilization, histological organization of the intestinal mucosa, activity of oxidative stress enzymes (catalase, glutathione S-transferase, glutathione peroxidase, and glutathione reductase) in the intestine, and nonspecific serum immune parameters (lysozyme and bactericidal activity). Results from this study indicated that dietary SDPP promoted fish growth in terms of BW and length; fish fed 3% SDPP were 10.5% heavier (P < 0.05) than those fed the control diet. Spray-dried plasma from porcine blood modulated the activity of the antioxidative defenses in the intestine (P < 0.05) and increased the density of goblet cells in the intestine (P < 0.05) and benefited the host by providing an effective immune barrier against gut pathogenic microbiota. The nonspecific serum immune response in fish fed diets with SDPP was greater (P < 0.05) than in fish fed the control diet. These results indicated that the inclusion of SDPP in gilthead sea bream feed could be beneficial for the fish by enhancing intestinal and serum innate immune function and the activity of antioxidative stress enzymes of the intestine and promoting growth performance.

Thermofluidynamics of the multiphase flow inside cylindroconical fermenters with different scales

In this work the experimental investigations of the flow and the temperature field during the fermentation of beer in cylindroconical tanks are presented. The flow stability is affected of the height/diameter ratio. Increasing the ratio leads to an unsteady, three-dimensional flow with several smaller vortices. In the course of our research the experiments have been performed with real fermentation fluid (wort) under various height/diameter ratio. In the study, two tanks have been used in the laboratory and on an industrial scale, which were equipped with special design features. The velocity fields during a real fermentation process are measured by means of Ultrasound Doppler Velocimetry. It permits measurements in opaque fluids. Furthermore temperature measurements are conducted to analyse the interrelationship between the heat transfer and flow structure.

Growth rates of larval and juvenile bigeye scad Selar crumenophthalmus in captivity

Growth rates of larval and juvenile bigeye scad Selar crumenophthalmus reared in captivity were studied. The results are presented, discussed, and compared to wild S. crumenophthalmus and other pelagic fish. S. crumenophthalmus are a small pelagic carangid fish of circumtropical distribution. Larvae were reared in a modified mesocosm system and sampled daily for growth. Larvae grew to a mean size of 4.74 cm (Standard Length) and 1.30 g by 45 days post hatch (dph). Larval length-at-age was best described by the exponential equation Y = 1.966e0.0704t. For juvenile growth trials, 1940 fish were stocked into four 2.5 m3 cylindro-conical tanks at two different densities (262 fish m-3 and 120 fish m-3) and reared from 45 dph to subadult stage. Fish were sampled daily for growth. No statistically significant differences in growth or survival were detected between tanks. Mean length and weight at 141 dph was 13.24 cm (Total Length) and 25.20 g. Juvenile length-at-age was best described by the Von Bertalanffy Growth Model equation Lt = 27.75(1 – e-0.03(t-1.57)). Weight-at-age was best described by a linear equation Wt = 1.7313x + 12.4662. The exponent of the length-weight equation was 3.14. In addition to providing the first published description of larviculture and juvenile growout techniques for S. crumenophthalmus, this study contains the first published data on this species’ larval growth and directly confirms estimates of S. crumenophthalmus juvenile growth done by other researchers using indirect techniques such as otolith daily growth increment and frequency distribution analysis.

Bacillus cereus var. toyoi promotes growth, affects the histological organization and microbiota of the intestinal mucosa in rainbow trout fingerlings1

In this preliminary study, we evaluated the effects of a gram-positive soil bacteria Bacillus cereus var. toyoi on the growth performance, digestive enzyme activities, intestinal morphology, and microbiota in rainbow trout Oncorhynchus mykiss fingerlings. Trout were maintained in a recirculation system and fed 2 diets: 1) a commercial trout feed deprived of the probiotic and 2) the same diet but with the spores of the probiotic bacteria dissolved in fish oil during the manufacturing of the feed (final concentration = 2 × 10(4) cfu/g). Each diet was tested in three 400-L cylindroconical tanks (125 fish per tank; initial density = 1.3 kg/m(3); 13.2°C) for a period of 93 d. The probiotic-supplemented diet promoted growth, and the final mean BW and standard length in fish fed the probiotic were 3.4% and 2.1%, respectively, which was greater than the control group (P < 0.05). Fish fed the probiotic showed a more homogeneous distribution in the final BW, with a greater frequency of individuals around the modal of the normal distribution of the population. This result is of practical importance because homogenous production lots can improve rearing practices, reducing hierarchical dominance situations arising from individuals of larger sizes. In addition, the probiotic-supplemented diet increased the level of leukocyte infiltration in the lamina propria of the intestinal mucosa, the number of goblet cells (P < 0.010), and villi height (P < 0.001) but did not affect villi width. The administration of the probiotic changed the intestinal microbiota as indicated by 16S rDNA PCR-restriction fragment length polymorphism. In this sense, fish fed the probiotic formed a well-defined cluster composed of 1 super clade, whereas compared control fish had a greater degree of diversity in their gut microbiota. These changes in gut microbiota did not affect the specific activity of selected pancreatic and intestinal digestive enzymes. These results indicate that the inclusion of the probiotic bacteria in trout feeds could be beneficial for the host by enhancing its intestinal innate immune function and promoting growth.

Influences of food particle size on growth, size heterogeneity, food intake and gastric evacuation in juvenile Nile tilapia, Oreochromis niloticus, L., 1758

This study aimed at determining the food particle sizes (diameter) that produce the fastest growth (S opt) in juvenile Nile tilapia, and modeling the growth penalties for particles departing from S opt. Three 14-day experiments were run with 3, 7 and 11 g juveniles, which were raised in 120-L flow-through cylindro-conical tanks at 29 ± 1 °C, fed at the optimum feeding level (R opt) and weighed at weekly intervals. In each experiment, four different sizes of pellets (diameter) were evaluated (0.5-mm intervals, 1.0–3.5 mm; three replications per pellet size). At the end of each experiment, food intake and gastric evacuation rate were determined by radiographic methods following the use of ballotini labelled feed. The results indicate that i) in all experiments, specific growth rates (SGRs) are significantly depressed for the largest particles; ii) S opt increases with increasing fish size (1.4 mm at 3 g, to 2.5 mm at 20 g); iii) the optimum particle size relative to mouth width (MW) varies only slightly with fish size (28 to 25% MW from 3 to 20 g); iv) growth heterogeneity is proportional to food particle size; and, v) food intake and gastric evacuation rates are inversely proportional to food particle size. A growth model (SGR) was constructed with a stepwise multiple-regression analysis against fish size, feeding level and food particle size (R 2 = 0.853, df = 71). For a particular fish size, the growth-to-particle size relationship is a log–log second order polynomial, which implies that the growth penalty is more severe when fish are fed small than large particles. By contrast, application of food particles slightly smaller than S opt tends to minimize growth heterogeneity. As fish size increases, the width of the SGR-to-S relationship broadens; so, the penalty for distributing particles departing from S opt is lower, and feeding strategies are facilitated.

Treatment of shrimp effluent by sedimentation and oyster filtration using Crassostrea gigas and C. rhizophorae

Efficiency in removing particulate matter from Litopenaeus vannamei shrimp culture effluent was assessed in laboratory scale employing sedimentation and oysters Crassostrea gigas and C. rhizophorae filtration processes. Cylindroconical tanks (100 L) were used in duplicate for sedimentation and 50-L in triplicate for oyster filtration. Fifteen oysters of each species weighing 76-80 g were stocked in each of the filtration treatment experimental units (biomass of 1065 - 1174 g oyster per unit). The control treatment was a tank similar to those used in the filtration treatment but with empty oyster shells. Hydraulic retention time of the effluent was of 6 hours in each treatment. First, effluent went through sedimentation, and then the supernatant went through the filtration tanks. Temperature, pH, dissolved oxygen, salinity, turbidity, total suspended solids, total volatile solids, chlorophyll a and BOD5 were evaluated. During sedimentation and filtration, temperature, pH, salinity and dissolved oxygen concentration remained stable. Sedimentation removed 18, 5.6, 27.5, 45.40 and 23.2% of turbidity, total suspended solids, total volatile solids, chlorophyll a and BOD5, respectively. Chlorophyll a and BOD5 after sedimentation presented significant difference (P&lt;0.05) from the farm crude effluent. For the filtration treatment, C. rhizophorae was more efficient removing 62.1, 70.6, 36.1, 100 and 17.2% of turbidity, total suspended solids, total volatile solids, chlorophyll a and BOD5, respectively, whereas C. gigas removed 56.3, 41.2, 27.8, 51.4 and 8.0% of the same parameters. Statistically comparing C. rhizophorae and C. gigas performances, there were differences (P&lt;0.05) in removing total suspended solids, total volatile solids and chlorophyll a.

Continuous Beer Fermentation Using Immobilized Yeast Cell Bioreactor Systems

Traditional beer fermentation and maturation processes use open fermentation and lager tanks. Although these vessels had previously been considered indispensable, during the past decades they were in many breweries replaced by large production units (cylindroconical tanks). These have proved to be successful, both providing operating advantages and ensuring the quality of the final beer. Another promising contemporary technology, namely, continuous beer fermentation using immobilized brewing yeast, by contrast, has found only a limited number of industrial applications. Continuous fermentation systems based on immobilized cell technology, albeit initially successful, were condemned to failure for several reasons. These include engineering problems (excess biomass and problems with CO(2) removal, optimization of operating conditions, clogging and channeling of the reactor), unbalanced beer flavor (altered cell physiology, cell aging), and unrealized cost advantages (carrier price, complex and unstable operation). However, recent development in reactor design and understanding of immobilized cell physiology, together with application of novel carrier materials, could provide a new stimulus to both research and application of this promising technology.

Optimised Acidification Power Test of Yeast Vitality and its Use in Brewing Practice

The optimised acidification power test (APT) of brewer's yeast quality includes storing the yeast slurry at 2°C under beer (AP remains constant for up to 6 days), a 15 min sample equilibration to room temperature, decantation, and washing by triple centrifugation in deionised water. The final yeast pellet keeps its AP for up to 6 h at room temperature under water and thus the APT does not need to be performed immediately after yeast collection. The correct AP value (maximum acidification produced by given yeast) is determined at 25 ± 0.1°C in a 15 mL sample containing ≥5% glucose and ≥1.5 g yeast wet weight. The cell concentration is conveniently measured as absorbance (A660). Cell flocculation and/or sedimentation that can distort APT results can be prevented by stirring the sample at ≥200 rpm. The AP of yeast of different generations used to pitch brewery fermentations in cylindroconical tanks had a very low correlation with the wort half-attenuation time (T1/2) due to large scatter, while each yeast generation separately showed a clear T1/2-AP relationship. The lowest AP of yeast cropped from cylindroconical tanks was displayed by the first cropped fraction. Post-cropping cooling had no effect on AP. Variations in pitching yeast vitality and their effect on the outcome of a brewery fermentation can be masked by variations in pitching rate, wort composition, ambient conditions in the cylindroconical tanks and other factors.

DIGESTIBILITY OF SELECTED FEED INGREDIENTS FOR TIGER GROUPER, Epinephelus fuscoguttatus

&lt;p&gt;The apparent digestibility (AD) of eight feed ingredients are widely available in Indonesia was determined. In each of two 5x5 latin-square experimental, tiger grouper &lt;em&gt;Epinephelus fuscoguttatus&lt;/em&gt; juveniles (100—150 g) were fed a reference diet and four test diets in accordance with the latin-square design. Test feed ingredients were substituted at rates of 40% for animal meals or 30% for plant meals. Chromic oxide was used as the digestibility marker. In determining the ingredient AD, the substitution ratio was calculated as the proportion of the nutrient (or energy) contributed by the test ingredient on an ‘as-is’ basis. Digestibility tanks were steeply slope 200 L cylindroconical tanks with a bottom outlet to facilitate faecal collection, which was carried out at 3-hourly intervals throughout the day. Each collection period took 5—7 days with a similar acclimatization time between diets. A combined ANOVA of the data for both experimental showed no difference (P&amp;gt;0.05) in the AD’s for each reference diets. Thus for comparative purpose, the derived AD’s of the test ingredients were analysed as a single ANOVA. The digestibility of animal meals was generally high (&amp;gt;59% for dry matter, &amp;gt;83% for protein, &amp;gt;65% for lipid, and &amp;gt;70 for gross energy) while that of plant meals was slow (&amp;lt;53% for dry matter, &amp;lt;53% for protein, &amp;lt;66% for lipid, and &amp;lt;46% for gross energy). This information will enable grow-out feeds for tiger grouper to be formulated on a least-cost digestible nutrient basis.&lt;/p&gt;

The effect of trigger depth on self-feeder utilisation, growth and the vertical distribution of tank-held rainbow trout Oncorhynchus mykiss (Walbaum)

This study investigated the effect of placing a self-feeding trigger at either a) 1 cm below the water surface or b) mid-water (35 cm below the surface), on self-feeder usage, growth, feed wastage and fin damage of juvenile rainbow trout, Oncorhynchus mykiss (Walbaum). The vertical distribution of trout was also measured for the first 31 days of self-feeding. Group-held trout (n=10 fish group−1, 5 groups treatment−1), weighing 51.06 g±8.09 g (mean±SD) were held in 200 l cylindroconical tanks (depth=75 cm) for 62 days. Trigger placement had no significant effect upon self-feeder conditioning, and upper trigger group (UTG) and lower trigger group (LTG) fish took an average of 16±7.4 days and 14±9.8 days to reach a stable level of self-feeding, respectively. Specific growth rate was significantly higher in UTG fish (1.83±0.20 vs. 0.95±0.21 for UTG vs. LTG fish, respectively) whilst condition factor and self-feeder utilisation (ration size, 1.21±0.18 vs. 0.52±0.15 kg tank−1 for UTG vs. LTG fish) were also significantly higher in UTG fish. Trigger depth had no significant effect on size heterogeneity, mortality, feed wastage, feed conversion ratio (FCR) or the incidence of caudal and dorsal fin splitting and fin erosion. Dorsal fin splitting decreased with time in UTG but not in LTG fish. Caudal fin erosion increased with time in UTG (upper lobe only) and LTG (both lobes). The vertical distribution of fish also differed between treatments and more LTG fish preferred the lower part of the tank. Placing a self-feeding trigger at a mid-water depth can significantly limit growth, condition factor and self-feeder utilisation in juvenile rainbow trout, in addition to hindering recovery from dorsal fin erosion.

Effect of stocking density on survival and growth performance of pikeperch, Sander lucioperca (L.), larvae under controlled conditions

The effect of stocking density on the survival and growth of pikeperch, Sander lucioperca (L.), larvae was examined in two consecutive experiments. In experiment I, 4-day-old larvae [body wet weight (BW): 0.5 mg; total body length (TL): 5.6 mm] were reared in 200-l cylindro-conical tanks in a closed, recirculating system (20 ± 0.5°C) at three stocking densities (25, 50 and 100 larvae l−1) and fed a mixed feed (Artemia nauplii and Lansy A2 artificial feed) for 14 consecutive days. At densities of 25 and 100 larvae l−1, growth rate and survival ranged from 2.7 to 1.9 mg day−1 and from 79.2 to 72.3%, and fish biomass gain ranged from 0.6 to 2.0 g l−1, respectively. There were two periods of increased larval mortality: the first was at beginning of exogenous feeding and the second during swim bladder inflation. In experiment II, 18-day-old larvae (BW: 35 mg; TL: 15.6 mm) obtained from experiment I were reared under culture conditions similar to those of experiment I, but at lower stocking densities (6, 10 and 15 larvae l−1). The fish were fed exclusively with artificial feed (trout starter) for 21 consecutive days. At densities of 6 and 15 larvae l−1, the growth rate and fish biomass gain ranged from 28.8 to 23.1 mg day−1 and from 2.0 to 3.3 g l−1, respectively. The highest survival (56.5%) was achieved at a density of 6 larvae l−1. Mortality at all densities was mainly caused by cannibalism II type behaviour (27–35% of total). In both experiments, growth and survival were negatively correlated and fish biomass gain positively correlated with stocking densities. The present study suggests that the initial stocking density of pikeperch larvae reared in a recirculating system can be 100 individuals l−1 for the 4- to 18-day period post-hatch and 15 individuals l−1 for the post-19-day period.