Nutritional Evaluation of Crambe Meal as a Partial Replacement of Soybean Meal in Nile Tilapia Diets

This study evaluated the apparent digestibility coefficient (ADC) of crambe meal (CM) and its potential to partially replace soybean meal (SM) protein in Nile tilapia diets. The ADC for dry matter, crude protein, ether extract, energy, amino acids, calcium and phosphorus of CM were assessed in fish (n=80; 65.30 ± 5.32 g). Subsequently, an 80-day feeding trial was conducted with Nile tilapia (n=140; 6.04 ± 0.25 g) randomly distributed in 20 experimental cages (70 L; seven fish cage-1) allocated in five circular tanks (1000 L) in recirculation water system, to evaluate the effects of replacement of SM by CM (0, 6, 12, 18 and 24% in isonitrogenous and isoenergetic diets) on growth, blood parameters, fillet yield and proximal composition. The CM shows good digestibility of protein (0.824) and amino acids (0.844) by Nile tilapia and its inclusion in the diet does not affect carcass and fillet yield or proximal composition. Fish fed diets with 24.0% of the SM replaced by CM showed the worst weight gain and feed conversion rate. The protein efficiency ratio decreased in fish fed diets with 12.0, 18.0 and 24.0% of the SM replaced by CM. Hemoglobin, mean corpuscular hemoglobin concentration, total plasma protein, glucose and alanine aminotransferase enzyme activity trend to increase at highest levels of CM in the diet. In conclusion, CM has potential to replace SM in Nile tilapia diets, due to high digestibility of protein and amino acids. However, anti-nutritional factors present in untreated CM interfere on the growth and nutrient utilization of Nile tilapia.

Biofortified Diets Containing Algae and Selenised Yeast: Effects on Growth Performance, Nutrient Utilization, and Tissue Composition of Gilthead Seabream (Sparus aurata)

Efforts have been made to find natural, highly nutritious alternatives to replace fish meal (FM) and fish oil (FO), which can simultaneously promote fish health and improve the nutritional quality of filets for human consumption. This study evaluated the impact of biofortified diets containing microalgae (as replacement for FM and FO), macroalgae (as natural source of iodine) and selenised yeast (organic source of selenium) on gilthead seabream growth, nutrient utilization, tissue composition and gene expression. A control diet (CTRL) with 15% FM and 5.5% FO was compared with three experimental diets (AD1, AD2, and AD3), where a microalgae blend (Chlorella sp., Tetraselmis sp., and DHA-rich Schizochytrium sp.) replaced 33% of FM. Diet AD1 contained 20% less FO. Diets were supplemented with Laminaria digitata (0.4% AD1 and AD2; 0.8% AD3) and selenised yeast (0.02% AD1 and AD2; 0.04% AD3). After feeding the experimental diets for 12 weeks, growth was similar in fish fed AD1, AD2, and CTRL, indicating that microalgae meal can partially replace both FM and FO in diets for seabream. But AD3 suppressed fish growth, suggesting that L. digitata and selenised yeast supplementation should be kept under 0.8 and 0.04%, respectively. Despite lower lipid intake and decreased PUFAs bioavailability in fish fed AD3, compared to CTRL, hepatic elovl5 was upregulated resulting in a significant increase of muscle EPA + DHA. Indeed, filets of fish fed AD2 and AD3 provided the highest EPA + DHA contents (0.7 g 100 g–1), that are well above the minimum recommended values for human consumption. Fish consuming the AD diets had a higher retention and gain of selenium, while iodine gain remained similar among diets. Upregulation of selenoproteins (gpx1, selk, and dio2) was observed in liver of fish fed AD1, but diets had limited impact on fish antioxidant status. Overall, results indicate that the tested microalgae are good sources of protein and lipids, with their LC-PUFAs being effectively accumulated in seabream muscle. Selenised yeast is a good fortification vehicle to increase selenium levels in fish, but efforts should be placed to find new strategies to fortify fish in iodine.

Effects of stand age and soil organic matter quality on soil bacterial and fungal community composition in Larix gmelinii plantations, Northeast China

It is of great interest to elucidate the biogeographic patterns of soil microorganisms and their driving forces, which is fundamental to predicting alterations in microbial-mediated functions arising from environment changes. Although the vertical movement of dissolved organic matter (DOM) drives the cycle of nutrients such as soil carbon but, in the restored ecosystem, the relationship between DOM and soil microbial nutrient utilization remains to be determined. Here, we investigated the changes of soil microbial community at 0-40 cm depth profile in three stages (10-, 30-, 50-years) of succession in Larix olgensis plantations and the fluorescence spectrum composition of DOM. With the increase of soil depth, the signal source of microorganisms increases. In a coniferous forest soil environment, the possible main source of DOM in deep soil is the production of microbial metabolism. Difficulty in the decomposition of organic matter determines the distribution and composition of microorganisms. Increasing forest age makes bacteria and fungi more specific and bacterial-fungal associations greater. Overall, our work contributes to the understanding of factors underlying microbial community distribution in plantation forests and the importance of DOM quality in building microbial communities.

Genome-Wide Identification of bZIP Transcription Factor Genes and Functional Analyses of Two Members in Cytospora chrysosperma

The basic leucine zipper (bZIP) transcription factor (TF) family, one of the largest and the most diverse TF families, is widely distributed across the eukaryotes. It has been described that the bZIP TFs play diverse roles in development, nutrient utilization, and various stress responses in fungi. However, little is known of the bZIP members in Cytospora chrysosperma, a notorious plant pathogenic fungus, which causes canker disease on over 80 woody plant species. In this study, 26 bZIP genes were systematically identified in the genome of C. chrysosperma, and two of them (named CcbZIP05 and CcbZIP23) significantly down-regulated in CcPmk1 deletion mutant (a pathogenicity-related mitogen-activated protein kinase) were selected for further analysis. Deletion of CcbZIP05 or CcbZIP23 displayed a dramatic reduction in fungal growth but showed increased hypha branching and resistance to cell wall inhibitors and abiotic stresses. The CcbZIP05 deletion mutants but not CcbZIP23 deletion mutants were more sensitive to the hydrogen peroxide compared to the wild-type and complemented strains. Additionally, the CcbZIP23 deletion mutants produced few pycnidia but more pigment. Remarkably, both CcbZIP05 and CcbZIP23 deletion mutants were significantly reduced in fungal virulence. Further analysis showed that CcbZIP05 and CcbZIP23 could regulate the expression of putative effector genes and chitin synthesis-related genes. Taken together, our results suggest that CcbZIP05 and CcbZIP23 play important roles in fungal growth, abiotic stresses response, and pathogenicity, which will provide comprehensive information on the CcbZIP genes and lay the foundation for further research on the bZIP members in C. chrysosperma.

Utilization of spent millet from locally fermented drink (Burukutu) as experimental diets for Clarias gariepinus

Brewer’s waste is one of the promising carbohydrate and protein source by-products for fish diets. A 10-wk feeding trial experiment involving 10 different diets (10 diets for Spent millet, from locally fermented drink (Burukutu) with increasing levels of brewer’s waste (40% crude protein) was carried out to evaluate the use of spent millet, from Burukutu production in Clarias gariepinus diets in place of normal Corn. Growth performance was compared against a control diet formulated to have similar composition to a typical commercial diet. 10 experimental diets replaced successively 0%, 10%, 20%, 30%, 40%, 50%, 70%, 80%, 90%, and 100% of the Corn carbohydrate with Spent millet from locally fermented drink, Burukutu.. The diets were isonitrogenous and isocaloric. A relatively good growth performance and nutrient utilization by Clarias gariepinus fed the test diets were observed. However, the results showed significant difference (p<0.05) in weight gain, SGR, FCR and RGR between treatments, with the control performing best. The result also showed that survival rate was high in all the treatment which indicate that, spent millet from burukutu production has no adverse effect on the experimented fish. Based on this research, it wasconcluded that 50% of the corn carbohydrate in a typicalcommercial diet could be replaced with spent grain (millet) from locally fermented drink (BKT) withno adverse effect on growth and feed utilization for Clarias gariepinus.

The MocR/GabR Ectoine and Hydroxyectoine Catabolism Regulator EnuR: Inducer and DNA Binding

The compatible solutes ectoine and 5-hydroxyectoine are widely synthesized by bacteria as osmostress protectants. These nitrogen-rich tetrahydropyrimidines can also be exploited as nutrients by microorganisms. Many ectoine/5-hydroxyectoine catabolic gene clusters are associated with a regulatory gene (enuR: ectoine nutrient utilization regulator) encoding a repressor protein belonging to the MocR/GabR sub-family of GntR-type transcription factors. Focusing on EnuR from the marine bacterium Ruegeria pomeroyi, we show that the dimerization of EnuR is mediated by its aminotransferase domain. This domain can fold independently from its amino-terminal DNA reading head and can incorporate pyridoxal-5′-phosphate (PLP) as cofactor. The covalent attachment of PLP to residue Lys302 of EnuR was proven by mass-spectrometry. PLP interacts with system-specific, ectoine and 5-hydroxyectoine-derived inducers: alpha-acetyldiaminobutyric acid (alpha-ADABA), and hydroxy-alpha-acetyldiaminobutyric acid (hydroxy-alpha-ADABA), respectively. These inducers are generated in cells actively growing with ectoines as sole carbon and nitrogen sources, by the EutD hydrolase and targeted metabolic analysis allowed their detection. EnuR binds these effector molecules with affinities in the low micro-molar range. Studies addressing the evolutionary conservation of EnuR, modelling of the EnuR structure, and docking experiments with the inducers provide an initial view into the cofactor and effector binding cavity. In this cavity, the two high-affinity inducers for EnuR, alpha-ADABA and hydroxy-alpha-ADABA, are positioned such that their respective primary nitrogen group can chemically interact with PLP. Purified EnuR bound with micro-molar affinity to a 48 base pair DNA fragment containing the sigma-70 type substrate-inducible promoter for the ectoine/5-hydroxyectoine importer and catabolic gene cluster. Consistent with the function of EnuR as a repressor, the core elements of the promoter overlap with two predicted EnuR operators. Our data lend themselves to a straightforward regulatory model for the initial encounter of EnuR-possessing ectoine/5-hydroxyectoine consumers with environmental ectoines and for the situation when the external supply of these compounds has been exhausted by catabolism.

Effect of Partial Soybean Replacement by Shrimp By-Products on the Productive and Economic Performances in African Catfish (Clarias lazera) Diets

The present study was carried out to evaluate the effects of partial replacement of soybean with shrimp by-products (SBp) in African catfish (Clarias lazera) diets on productive (growth, digestibility, body composition, dressing yield, blood parameters, immunity) and economic performances. Therefore, 750 fingerlings (~20.0 g) were distributed into five groups of 150 fingerlings/group with three replicates (n = 50) per group. Group 1 was fed a basal diet, while G2 and G3 were fed diets containing 25% SBp (autoclaved and acid-treated, respectively) as soybean replacer for 12 weeks, while, in G4 and G5, SBp level was 50%. All growth and nutrient utilization parameters (body weight, Wg, ADG, PER, FCR, and digestibility), plasma proteins, and immunity significantly increased in G4 and G5. Anemia screening markers recorded insignificant differences between the tested groups and control one, whereas lipid markers of plasma and fish body decreased by autoclaved SBp and increased by acid-treated SBp. The African catfish body dry matter and crude protein percentages were enriched by the addition of SBp. Replacing the soybean meal decreases diet costs and diet costs/1 kg of weight gain. In conclusion, replacing soybean with SBp (especially 50% acid-treated) positively influenced productive and economic performances with friendly effects to avoid the environmental pollution by these wastes.