Antimicrobial Power of Organic Acids and Nature-Identical Compounds against Two Vibrio spp.: An In Vitro Study

Effects of monoglycerides of short and medium chain fatty acids and cinnamaldehyde blend on the growth, survival, immune responses, and tolerance to hypoxic stress of Pacific white shrimp (Litopenaeus vannamei)

Free fatty acids have long been used as dietary supplements in aquaculture, but the application of monoglycerides has increased interest in more recent times. The study aimed to investigate the effects of dietary short- and medium-chain fatty acid monoglyceride and cinnamaldehyde (SMMG) on the growth performance, survival, immune responses, and tolerance to hypoxic stress of Pacific white shrimp (Litopenaeus vannamei). In Experiment 1, shrimp post-larvae were divided into 4 groups with 6 replicates and fed with diets supplemented with 0 (control), 0.3, 0.4, and 0.5% diet for 30 days. The final body weight and survival rate were determined. In Experiment 2, the juvenile shrimp from Experiment 1 were subjected to hypoxic stress conditions (dissolved oxygen level 2-2.5 mg/L) for 14 days, then the specific growth rate (SGR), survival rate, intestinal Vibrio spp. count, immune responses, and histopathological change of the hepatopancreas were analyzed. Following the 30-day feeding trial, the results revealed that the final body weight and survival of the 0.3-0.5% SMMG groups (2.81-3.06 g and 74.00-84.33%, respectively) were significantly higher than the control shrimp (1.96 g and 68.33%, respectively). In the hypoxic stress experiment, the survival rates of shrimp fed 0.4-0.5% SMMG (71.67-80.00%) were significantly higher than the control (51.67%). Although the SGR were not affected by SMMG supplementation, all immune parameters evaluated were significantly enhanced, and the intestinal Vibrio spp. counts were significantly decreased in the 0.4-0.5% SMMG-fed shrimp; the histopathological structure of the hepatopancreas was also improved in these shrimp compared to the control. Our findings indicated that SMMG as a feed additive has beneficial effects in improving shrimp health and increasing tolerance to hypoxic conditions.

Synergistic antimicrobial system based on nisin and α-hydroxy organic acids

Synergistic antimicrobial is a promising way to overcome microbial contamination in food and drugs. In the study, the synergistic effect between nisin and α-hydroxy organic acids on E. coli and S. aureus was investigated. The experimental results showed that the combined antibacterial ability of nisin-citric acid system was the most prominent. The FCI index also indicated that the combination of nisin and citric acid had synergistic effects on E. coli. When nisin was combined with citric acid, the inhibition rates of E. coli and S. aureus were increased to 4.43 and 1.49 times, respectively. Nisin-citric acid complex system could effectively slow down the proliferation of S. aureus and E. coli at lower concentrations, and can quickly destroy the cell membrane after 4 h of action. Therefore, the combination of nisin and citric acid is expected to be a potential solution for food and drug preservation.

Antimicrobial activity and chemical profile of wood vinegar from eucalyptus (Eucalyptus urophylla x Eucalyptus grandis - clone I144) and bamboo (Bambusa vulgaris)

Microbial resistance to drugs is a public health problem; therefore, there is a search for alternatives to replace conventional products with natural agents. One of the potential antimicrobial agents is wood vinegar derived from the carbonization of lignocellulosic raw materials. The objectives of the present work were to evaluate the antibacterial and antifungal action of two kinds of wood vinegar (WV), one of Eucalyptus urograndis wood and another of Bambusa vulgaris biomass, and determine their chemical profile. The antimicrobial effect was assessed against Staphylococcus aureus, Pseudomonas aeruginosa, Salmonella enteritidis, Escherichia coli, Streptococcus agalactiae, and Candida albicans. The minimum inhibitory concentration and the minimum bactericidal and fungicidal concentrations were determined. Micrographs of the microorganisms before and after exposure to both kinds of wood vinegar were obtained by scanning electron microscopy. The chemical profile of the eucalyptus and bamboo vinegar was carried out by gas chromatography and mass spectrometry (GC/MS). Both types of WV presented significant antimicrobial activity, with the bamboo one having a higher efficiency. Both studied pyroligneous extracts seem promising for developing natural antimicrobials due to their efficiency against pathogens. GC/MS analyses demonstrated that the chemical profiles of both kinds of WV were similar but with some significant differences. The major component of the eucalyptus vinegar was furfural (17.2%), while the bamboo WV was phenol (15.3%). Several compounds in both WVs have proven antimicrobial activity, such as acetic acid, furfural, phenol, cresols, guaiacol, and xylenols. Together, they are the major in the chemical composition of the organic fraction of both WVs. Bamboo vinegar had a more expressive content of organic acids. Micrographs of microorganisms taken after exposure to both kinds of wood vinegar displayed several cell modifications. The potential of both types of wood vinegar as a basis for natural antimicrobial products seems feasible due to their proven effect on inhibiting the microorganisms' growth assessed in this experiment.

Ameliorative role of dietary acidifier potassium formate on growth metrics, blood chemistry, gut health and well-being indices of rohu, Labeo rohita fingerlings

Organic acids and their derivatives have been attributed to growth and well-being improvement in fish when supplemented in their diets. Therefore, this study was conducted to evaluate the ameliorative role of potassium formate (PF) in rohu Labeo rohita fingerlings. A total of 240 healthy rohu fingerlings (9.0 ± 0.5 g ± SE) were randomly divided into four equal groups in triplicates. Fish were fed with isonitrogenous feeds: PF10 (10 g PF/kg), PF20 (20 g PF/kg) and PF30 (30 g PF/kg). Feed without PF supplementation served as control. The results indicated that the specific growth rate (SGR) and feed conversion ratio (FCR) were significantly (p<0.05) higher in PF10. Total serum globulin content was found significantly (p<0.05) elevated in PF10 after the bacterial challenge. Non-specific lysozyme activity was significantly higher (p<0.05) after the challenge. The digestive protease enzyme activity was significantly (p<0.05) improved in PF10 treatment. Additionally, the digestive morphology of the treated fish was seen to be improved. Greater villus area, increased villus number, reduced lumen space in the hindgut, reduced vacuolation in mucosal folds and proliferation of goblet cells-like changes were observed in the PF-supplemented fish. Significantly (p<0.05), a higher relative percentage of survival (RPS) was observed in PF10 and PF20 treatments. The study revealed that the dietary supplementation of rohu fingerlings with lower levels of potassium formate could enhance the nutritional efficiency and physiological activities of rohu fingerlings. This study serves as a baseline for future research on the application of formic acid derivatives and other acidifiers in carp culture.

Modulatory effect of Gracilaria gracilis on European seabass gut microbiota community and its functionality

Seaweeds are an important source of nutrients and bioactive compounds and have a high potential as health boosters in aquaculture. This study evaluated the effect of dietary inclusion of Gracilaria gracilis biomass or its extract on the European seabass (Dicentrarchus labrax) gut microbial community. Juvenile fish were fed a commercial-like diet with 2.5% or 5% seaweed biomass or 0.35% seaweed extract for 47 days. The gut microbiome was assessed by 16S rRNA amplicon sequencing, and its diversity was not altered by the seaweed supplementation. However, a reduction in Proteobacteria abundance was observed. Random forest analysis highlighted the genera Photobacterium, Staphylococcus, Acinetobacter, Micrococcus and Sphingomonas, and their abundances were reduced when fish were fed diets with algae. SparCC correlation network analysis suggested several mutualistic and other antagonistic relationships that could be related to the predicted altered functions. These pathways were mainly related to the metabolism and biosynthesis of protective compounds such as ectoine and were upregulated in fish fed diets supplemented with algae. This study shows the beneficial potential of Gracilaria as a functional ingredient through the modulation of the complex microbial network towards fish health improvement.

Nature-identical compounds as feed additives in aquaculture

Aquaculture sustainable development is necessary since it is categorized as the most important source of aquatic products for human consumption and it is expected to keep growing shortly. For this reason, the addition of natural immunostimulants to fish diet to improve fish health and to preserve the environment have great importance in aquaculture. In this sense, new biotechnological tools as nature-identical compounds are now being used as feed additives to strengthen and stimulate the fish immune system to prevent and/or control diseases due to their lesser cost and higher availability than plant compounds. This review aims to present the most recent studies in which nature-identical compounds have been used in the fish diet to establish their possible use in aquaculture. Nature-identical compounds can be considered a promising alternative to be added to fish diets to promote growth performance, manipulate the gut microbiota, and improve the immune and oxidative status of fish as wells as control bacterial infections in this important aquatic industry.

Chemical-Based Methodologies to Extend the Shelf Life of Fresh Fish-A Review

Due to its characteristics, fresh fish is a highly perishable food with a very short shelf-life under refrigeration. Several methods have been introduced to slow down its deterioration, such as by means of oxygen depletion of the food package (vacuum packaging), or by changing the natural atmosphere that is in contact with the fresh fish (modified atmosphere packaging), or by the use of chemicals generally recognized as safe: such compounds can be directly applied (by dipping or spraying) or incorporated into packaging materials and slowly migrate to the product, exerting a hurdle effect against microbial development and lipid oxidation (active packaging). This review aims to cover the most recent advances in chemical-based approaches for fresh fish preservation, applied either singly or in combination. Vacuum packaging, modified atmosphere, and active packaging preservation methodologies are presented, along with the inclusion of chemical additives, such as organic acids and natural extracts, and their combination with icing systems. Advantages and disadvantages of these methodologies and their impact on fresh fish quality and shelf-life are discussed, reaching the conclusion that both are positively influenced overall. Indeed, the contribution of chemical-based strategies for fresh fish preservation is undeniable, and is expected to be a research topic of increasing interest in the future.