Bacterial Single-cell Protein Research Articles

Replacement of Dietary Fish Protein with Bacterial Protein Results in Decreased Adiposity Coupled with Liver Gene Expression Changes in Female Danio rerio

BackgroundEffective use of Danio rerio as a preclinical model requires standardization of macronutrient sources to achieve scientific reproducibility across studies and labs. ObjectiveOur objective was to evaluate a bacterial-based single-cell protein (SCP) for the production of open-source standardized diets with defined health characteristics for the zebrafish research community. MethodsWe completed a 16-wk feeding trial using juvenile D. rerio 31 d postfertilization (10 tanks per diet and 14 D. rerio per tank) with formulated diets containing either a typical fish protein ingredient [standard reference (SR) diet] or a novel bacterial SCP source [bacterial protein (BP) diet]. At the end of the feeding trial, growth metrics, body composition, reproductive success, and bulk transcriptomics of the liver (RNAseq on female D. rerio with confirmatory rtPCR) were performed for each diet treatment. ResultsD. rerio fed the BP diet had body weight gains equivalent to the D. rerio fed fish protein, and females had significantly lower total carcass lipid, indicating reduced adiposity. Reproductive success was similar between treatments, suggesting normal physiological function. Genes differentially expressed in female D. rerio fed the BP diet compared with females fed the SR diet were overrepresented in the gene ontologies of metabolism, biosynthesis of cholesterol precursors and products, and protein unfolding responses. ConclusionProtein source substantially affected body growth metrics and composition as well as gene expression. These data support the development of an open-source diet utilizing an ingredient that correlates with improved health profiles and reduced variability in notable outcomes.

Effect of different types of bacterial single cell protein on feed intake, digestibility, growth and body composition of Pacific white shrimp (Penaeus vannamei)

This study assessed the potential of four bacterial (Methylococcus capsulatus) single cell protein (SCP) products as alternative protein sources for Pacific white shrimp (Penaeus vannamei) diets. A growth trial and a digestibility trial were undertaken, during which the bacterial SCP products were compared with a high-quality fishmeal and a soy protein concentrate, regarding their impact on ingredient digestibility, growth, feed intake and whole-body composition of juvenile P. vannamei. Seven diets were formulated; one reference diet (REF) and six test diets. The test diets consisted of 85% of the REF diet and 15% of a test ingredient. Ingredients tested were four bacterial SCP products (SCP1–4), which differed in processing conditions, fishmeal (FM) and soy protein concentrate (SoyProt). Growth and feed utilization were similar for P. vannamei fed either the FM diet or one of the bacterial SCP diets, whilst lowest growth and feed utilization were observed for shrimp fed the SoyProt diet. Final whole-body protein content did not differ between shrimp fed the FM diet or one of the four bacterial SCP diets. However, shrimp fed the SCP diets had a significantly higher final phosphorus body content and a higher phosphorus retention than shrimp fed the FM or SoyProt diets. This indicates a higher phosphorus availability in the bacterial SCP products compared to FM and SoyProt. Protein digestibility of the SCP products was similar to FM, whilst amino acid (AA) digestibility was comparable to FM for three of the four SCP products (SCP1, SCP2 and SCP4). The SCP3 product showed the lowest digestibility for most AA, indicating a possible influence of processing conditions on AA availability of bacterial SCPs. Overall, this study highlights that bacterial SCP originating from M. capsulatus is a viable alternative protein source for Pacific white shrimp diets, but processing conditions should be taken into account.

Nutritional innovations in superior gilthead seabream (Sparus aurata) genotypes: Implications in the utilization of emerging new ingredients through the study of the patterns of secretion of digestive enzymes

To promote sustainability and efficiency for aquaculture production, there are two key actions: i) The implementation of novel nutritional strategies with more sustainable raw materials, that aim to reduce the dependence on fishmeal (FM) and fish oil (FO) in the feeds, and ii) the implementation of a successful breeding program addressed to improve fish growth, feed utilization, and health. Different studies performed on salmonids and European sea bass (Dicentrarchus labrax) support the existence of genetic variability for the utilization of plant or non-marine-based diets. Nevertheless, those studies do not consider that the better zootechnical performance obtained in selected fish can be associated with differences in digestive biochemistry. Therefore, the present study aimed to evaluate the changes in the levels of the activities of different digestive enzymes present in two populations of gilthead seabream (Sparus aurata): reference or selected for high growth. Furthermore, the effect of different diets including a variety of protein ingredients partially substituting FM (poultry meal, insect meal, and bacterial single-cell protein) was assessed on the digestive enzyme profile of both fish genotypes, after 90 days of feeding. Higher levels of certain protein-related enzymes (pepsin and chymotrypsin) were found in selected sea bream fish compared with reference fish. Selected fish also revealed higher ADCs for dietary amino acids, irrespective of the diet fed, compared with the reference group. These results, added to the better growth and feed utilization of selected sea bream compared with reference fish, suggest that selected fish are more able to utilize the combination of emergent ingredients for aquafeeds, showing changes in the pattern of digestive enzymes to face the different ingredients in diets, which indicates a higher plasticity of the digestive enzymes to face changes in dietary ingredients. Those changes could be reflecting a compensatory mechanism to improve the digestibility of the ingredient.

Single cell protein from methanotrophic bacteria as an alternative healthy and functional protein source in aquafeeds, a holistic approach in rainbow trout (Oncorhynchus mykiss) juveniles

Bacterial single cell protein (BSCP) obtained from methanotrophic bacteria was tested as an alternative protein source to fishmeal (FM) in compound diets for rainbow trout (Oncorhynchus mykiss) juveniles (initial body weight, BW = 11.3 ± 0.2 g, mean ± standard deviation). Different levels of FM replacement (0, 25, 50, 75 and 100%) by a BSCP (0, 3.75, 7.5, 11.25 and 15% of Uniprotein® Aqua) were tested in isoproteic (crude protein: 42%) and isolipidic (crude fat: 21%) extruded diets. The trial was divided in two different parts, a nutritional trial that lasted 83 days during which the impact of experimental diets was evaluated in terms of key performance indicators (KPIs) associated to fish growth performance and feed utilization, which was followed by a challenge with a pathogenic bacterium (Aeromonas salmonicida subsp. salmonicida) to evaluate the immunological competence of fish fed the experimental diets (15 days). At the end of the nutritional trial, somatic growth in terms of body weight (BW) responded quadratically (P < 0.05) to the dietary inclusion of BCSP with the lowest BW values (183.4 ± 4.5 g) recorded in fish fed 100% FM replacement with BSCP, whereas the rest of dietary groups showed similar BW values (191.3–201.2 g). Feed intake was not affected by the level of FM replacement by BSCP, whereas feed conversion ratio (FCR) slightly increased with increasing levels of BSCP (P < 0.05), even though the lowest FCR values were found in fish fed 50% FM replacement by BSCP (0.79 ± 0.01) in comparison to the control group (0.81 ± 0.01). When using quadratic linear regression, the optimal dietary FM replacement by BSCP in terms of BW values was estimated as 41.7%. The nutritional quality of the fillet was not altered with experimental diets; all dietary groups showed similar amino acid levels as well as their content in HUFA n-3 and n-6 that remained unaltered (P > 0.05) and lipid nutritional indexes (P > 0.05). No negative effects were observed in the histological organization of the liver nor the proximate intestine, neither in the lipid peroxidation levels nor activity of antioxidative stress enzymes in the liver from fish fed increased inclusion levels of BSCP (P < 0.05). The replacement of FM by the tested BSCP obtained from methanotrophic bacteria did not cause an imbalance or dysbiosis in the intestinal microbiota in rainbow trout regardless of the level of FM replaced. The replacement of FM by BSCP at 50% improved disease resistance in rainbow trout exposed to furunculosis when compared to the control diet (cumulative mortality = 83.3 ± 7.2% vs. 49.2 ± 15.6%; P < 0.05), which suggested that this ingredient may also have some immunomodulatory properties that would protect fish from infections, although their mode of action deserves further attention. Current results indicated that the tested BSCP from methanotrophic bacteria is a safe, functional, and sustainable alternative protein source for aquafeeds.

Feeding gilthead sea bream with increasing dietary bacterial single cell protein level: Implication on growth, plasma biochemistry, gut histology, and gut microbiota

Bacterial single cell protein (SCP) is considered a promising circular protein ingredient for aquafeed, due to the high protein content, and for the possibilities to grow them on different substrates such as organic waste thus leading to low environmental footprint and affordable production costs. Their use as raw material has been assessed in several farmed species, however, research on Mediterranean ones is still scarce. Hence, a study was undertaken to evaluate growth, plasma biochemistry, gut histology and gut microbiota (GM) response of gilthead sea bream (Sparus aurata) fed diets with increasing levels of bacterial SCP in comparison to a control without SCP. Three isonitrogenous and isolipidic extruded diets (44% protein; 19% lipid) were formulated with different bacterial SCP (derived from Corinebacterium glutamicum) level (10% SCP, SPC10; 15% SCP, SCP15; 20% SCP, SCP20) to replace vegetable protein ingredients (total replacement of soy protein concentrate and partial replacement of corn gluten), while a control diet (CTRL) was formulated without SCP. Fish groups of 45 individuals (initial weight: 75 g) were fed to visual satiation over 108 days. At the end of the trial there were no significant differences on growth, feed intake, feed conversion rate, protein efficiency ratio and protein apparent digestibility. Most of plasma parameters were found to be equal for all treatments, except for those related to nucleic acids molecules degradation such as phosphorus and urea which were higher in SCP10 and SCP20 compared to CTRL, respectively. No morphological alterations were found in the intestines of any fish analysed. Different responses of the overall GM structure in relation to the bacterial SCP inclusion level were detected. Specifically, SCP exerted a positive effect on GM internal diversity which increased at increasing dietary SCP inclusion level. In addition, SCP inclusion lead to increase in the abundance of Bacillus spp., taxa which can potentially support nutrition, immune system, and disease resistance. In conclusion, it seems feasible to include up to 20% of SCP dietary level for gilthead sea bream without compromising growth, feed efficiency and health parameters.

Optimization of an effective growth medium for biomass production of Bacillus cereus

Protein is the main source of nutrition in fish feed. It is necessary to use bacterial single-cell protein (SCPs) as a substitute for conventional protein. This study aims to determine the effectiveness of tofu liquid waste as a growth medium for biomass production of Bacillus cereus as an SCPs. The isolates used were B. cereus SN7 and B. cereus consortium (combination of 5 isolates of B. cereus with different strains). The method used was experimental where isolates were cultured in a medium containing tofu liquid waste with different concentrations (8%, 10%, and 12%) enriched with 10% skim milk. Furthermore, the analysis of an effective growth medium was carried out by three methods, namely total plate count, optical density, and cell-dry weight. Cell biomass measurements were carried out for 24 hours with an observation time of every 6 hours. The results showed the best growth medium used in the culture of B. cereus SN7 and B. cereus consortium was tofu liquid waste at a concentration of 12% enriched with 10% skim milk. In conclusion, the cell mass of B. cereus SN7 and B. cereus consortium significantly increased at 6 to 12 hours.

Evaluation of a Bacterial Single-Cell Protein in Compound Diets for Rainbow Trout (Oncorhynchus mykiss) Fry as an Alternative Protein Source.

Simple SummaryFish meal (FM), as the main protein source, is used in aquafeeds due to its good nutritional profile and palatability. In recent years, because of the high cost and uncertainty in FM supply, studies have been focused to identify and evaluate alternative protein ingredients to minimize FM and reducethe cost of formulated feeds. Currently, plant protein ingredients and animal by-products are used as alternative protein sources to FM, but these components have some nutritional limitations, such as beingrich in anti-nutritional elements and deficient in certain essential amino acids. Among alternative protein sources, single-cell protein (SCP) such as bacteria, yeasts and microalgae, is considered a promising substitute for animal- or plant-derived ingredients. In this work, we aimed to evaluate the replacement of FM with a bacterial SCP, a by-product of the monosodium L-glutamic acid produced by microbial fermentation of vegetal raw materials, in diets for rainbow trout (Oncorhynchus mykiss) fry. Results indicated that the maximum replacement of FM by SCP in terms of growth and feed efficiency performance was up to 50%, while the broken-line regression analyses using DHA muscle content and weight gain showed that this value ranged between 46.9 to 52% SCP depending on the parameter considered.A 60-day trial was conducted in rainbow trout (Oncorhynchus mykiss) fry (initial weight = 2.5 ± 0.6 g) to evaluate the potential use of a bacterial single-cell protein (SCP) as an alternative protein source. Five experimental diets with different levels of fishmeal replacement (0, 25, 50, 75 and 100%) and no amino acid supplementation were tested. At the end of the trial, we found that fry fed diets, replacing 25 and 50% of fishmeal with bacterial SCP, were 9.1 and 21.8% heavier, respectively, than those fed the control diet (p < 0.05), while Feed Conversion Ratio (FCR) values were also lower in comparison to the reference group. These results were also supported by Protein Efficiency Ratio (PER) and Lipid Efficiency Ratio (LER) values that improved in fish fed diets replacing 50% fishmeal by bacterial SCP. The inclusion of SCP enhanced Feed intake (FI) (p < 0.05), although FI was reduced at higher inclusion levels (>50%), which was associated to feed palatability. High levels of bacterial SCP (>50%) affected the muscular amino acid and fatty acid profiles, imbalances that were associated to their dietary content. The broken-line regression analysis using muscle DHA content and weight gain data showed that the maximum levels of fishmeal replacement by bacterial SCP were 46.9 and 52%, respectively.

Long-term occupational outcomes of endotoxin exposure and the effect of exposure cessation

ObjectiveTo study the possible respiratory and haematological effects of endotoxin exposure to bacterial single-cell protein (BSCP) in workers during a follow-up period of 5 years including 4 years of exposure...

Occupational exposure to bacterial single cell protein induces inflammation in lung and blood

Bacterial single cell protein (BSCP) is used as a protein enrichment in livestock and fish feed, and is extracted from dried bacterial mass. In the production of BSCP, workers are exposed to organic dust containing high levels of endotoxins that may induce acute airway inflammation. However, the long term effect on the airways of such exposure is not known, and we have examined inflammatory markers in induced sputum and blood among BSCP exposed workers. We included 21 non-smoking production workers (age 31–42 (range; mean 35)) without respiratory symptoms and 21 healthy non-exposed references (age 21–52 (range; mean 34)). Airborne endotoxin concentrations were measured, and induced sputum samples and blood samples were collected from the workers and non-exposed references. The airborne endotoxin concentration measured in inhaled air during the work shift was 430 EU/m3 (50–2000) (median (range)). The percentage of neutrophils in induced sputum was 79% (66–93) (median (25th–75th percentiles)) and 31% (25–45) (p < 0.001) for operators and references, respectively. Protein analysis in induced sputum supernatant showed significantly elevated levels of interleukins IL-1β and IL-12 (p < 0.05), while blood analysis showed significantly elevated levels of PDGF-BB (platelet-derived growth factor-BB) and RANTES (regulated upon activation normally T cell expressed and secreted) (p < 0.05). Workers exposed to BSCP had an airway inflammation characterized by a high level of neutrophils. However, only a few cytokines were elevated in lung and blood, which could imply low inflammatory activity suggestive of possible adaptation mechanisms due to daily exposure to BSCP, or that the inflammation reaction was a dose-related response occurring at higher levels.

Circulating lipopolysaccharides in the blood from “bioprotein” production workers

Background: Workers producing bacterial single-cell protein (BSCP), “bioprotein,” are exposed to organic dust containing high levels of endoxins (lipopolysaccharides, LPS). Workers in this industry have complained of episodes of fever,...

Complement activation and cytokine response by BioProtein, a bacterial single cell protein

The bacterial single cell protein (BSCP), BioProtein, is dried bacterial mass derived from fermentation of the gram negative bacteria Methylococcus capsulatus, used for animal and fish feed. Workers in this industry suffer frequently from pulmonary and systemic symptoms which may be induced by an inflammatory reaction. The aim of the present study was to examine the effect of BSCP on inflammation in vitro as evaluated by complement activation and cytokine production. Human serum was incubated with BSCP and complement activation products specific for all pathways were detected by enzyme-linked immunosorbent assay (ELISA). Human whole blood anti-coagulated with lepirudin was incubated with BSCP and a panel of 27 biological mediators was measured using multiplex technology. BSCP induced a dose-dependent complement activation as revealed by a pronounced increase in alternative and terminal pathway activation (fivefold and 20-fold, respectively) at doses from 1 microg BSCP/ml serum and a similar, but less extensive (two- to fourfold) increase in activation of the lectin and classical pathways at doses from 100 and 1000 microg BSCP/ml serum, respectively. Similarly, BSCP induced a dose-dependent production of a number of cytokines, chemokines and growth factors in human whole blood. At doses as low as 0 x 05-0 x 5 microg BSCP/ml blood a substantial increase was seen for tumour necrosis factor (TNF)-alpha, interleukin (IL)-1-beta, IL-6, interferon (IFN)-gamma, IL-8, monocyte chemoattractant protein (MCP)-1, macrophage inflammatory protein (MIP)-1alpha, MIP-1beta, IL-4, IL-9, IL-17, IL-1Ra, granulocyte-colony-stimulating factor (G-CSF) and vascular endothelial growth factor (VEGF). Thus, BSCP induced a substantial activation of all three initial complement pathways as well as a pronounced cytokine response in vitro, indicating a potent inflammatory property of this agent.

Short term changes in lung function, leukocytosis in blood, and lachrymal fluid among bacterial single cell protein workers after an episode with high exposure to endotoxins

Aims: To study possible effects of endotoxin exposure among bacterial single cell protein workers on pulmonary function, blood parameters, and lachrymal fluid before and after a work shift. Methods: The...

Apparent absorption efficiencies of amino acids in rainbow trout, Oncorhynchus mykiss (Walbaum), fed diets containing bacterial single-cell protein

The aim of the present study was to compare the apparent absorption efficiency of individual indispensable and dispensable amino acids in diets containing varying proportions of bacterial single cell protein (BSCP) and fishmeal when fed to rainbow trout, Oncorhynchus mykiss (Walbaum). Four diets were formulated to contain a total of 45.8% crude protein, of which 0% was from BSCP in diet 1 (BSCP-0), 25% in diet 2 (BSCP-25), 62.5% in diet 3 (BSCP-62.5) and 100% in diet 4 (BSCP-100); the remainder of the protein was from fishmeal. The four diets were isonitrogenous and had similar amino acid compositions. Duplicate groups of 25 fish were fed one of the four experimental diets at the rate of 20 g kg−1 body weight per day for 132 days. Apparent absorption efficiency was measured over a 45-day period during the growth trial. Results from two methods of faeces collection and two indicators of absorption efficiency were compared. The amino acid absorption efficiency of BSCP-100 was significantly lower (P < 0.05) when compared to the other three diets and absorption of some of indispensable amino acids was below the requirement level. The variation seen in individual amino acids absorption efficiencies between diets suggests that this parameter may be important in fish nutritional investigations.

Feed consumption, growth and growth efficiency of rainbow trout (Oncorhynchus mykiss(Walbaum)) fed on diets containing a bacterial single-cell protein

The aim of the present study was to compare the nutritive value of bacterial single-cell protein (BSCP) with that of fishmeal in rainbow trout (Oncorhynchus mykiss (Walbaum)). Four diets were formulated to contain a total of 458 g crude protein/kg of which 0% was from BSCP in diet 1 (BSCP-0), 25% in diet 2 (BSCP-25), 62.5% in diet 3 (BSCP-62.5) and 100% in diet 4 (BSCP-100); the remainder of the protein was from fishmeal. There were two studies: in study 1, duplicate groups of twenty-five fish were fed on one of the four experimental diets at the rate of 20 g/kg body weight per d for 132 d. Feed consumption rates of individual fish were measured using radiography and the overall apparent absorption efficiency for N in each group was measured over a 2-week period. In study 2, N intake, consumption, absorption and accretion were measured for each fish under controlled environmental conditions (12 h: 12 h light-dark regime; 14 degrees). Higher dietary levels of BSCP resulted in significantly higher feed consumption rates but reduced N absorption efficiency and growth rates. However, a diet containing 25% BSCP (75% fishmeal) did not significantly influence growth rates, feed consumption and absorption efficiency compared with a 100% fishmeal diet. The N growth efficiencies were highest in fish fed on the diet containing the highest level of fishmeal and significantly decreased with increasing BSCP content. Construction of N budgets demonstrated that the reduction in growth in fish eating an increasingly larger proportion of BSCP was due to a decrease in N absorption and an increase in the excretion of urea.

Hydroxamate siderophore content of organic fertilizers

Abstract To estimate siderophore input into soil through fertilization, the hydroxamate siderophore content was determined in five organic fertilizers: granulated bacterial biomass (BAC); granulated fungal biomass (BIO); grape marc compost (BIV); chicken, dung (ITA); and bacterial single cell protein biomass (PRU). Siderophore content, expressed as Desferrioxamine B equivalents as determined by a modified version of the Arthrobacter flavescens JG‐9 bioassay, ranged from 0 to 20,647 ng g‐1 dry wt. of fertilizer (PRU < BIV < ITA < BAC < BIO). Recommended application rates of BIO would result in a calculated siderophore input of about 10 μg kg‐1 of soil in the plow layer. Such additions could affect iron nutrition of plants and alleviate of iron chlorosis.

Purine Availability and Metabolism in Dogs Fed Single-Cell Protein or RNA

For the evaluation of single-cell protein (SCP) the porportion of dietary purines made available by digestion and absorption was estimated with dogs (Dalmatian) in total urine collection experiments. The animals received a low purine control diet with 25% casein, diets with 25–100% replacement of casein by a bacterial SCP grown on methanol, and the control diet plus yeast RNA purine equivalent to SCP diet. Nucleic acids, bases, and purine metabolites were determined by reversed-phase high-pressure liquid chromatography. The quantitative influence of dietary purines (x) on renal purine excretion (y) was described by the equation (millimoles per day) y = 0.57x + 3.52 (r = 0.955) indicating the endogenous excretion rate of 3.5 mmol/day and the metabolic availability of 57% of ingested purines. As the ratio of urate to allantoin increased with purine intake, individual equations were established for both metabolites. On the control diet + RNA and SCP diet (100% replacement for casein), purine intakes of 20.0 and 18.2 mmol/day resulted in purine excretion values of 7.3 and 11.4 mmol/day (P < 0.05). The proportion of free bases in the latter diet appeared as the main reason for this difference. Other influences are discussed.purine metabolism single-cell protein nucleic acids dog

Lack of allergic reactions in workers exposed to Pruteen (bacterial single-cell protein).

Men exposed to high concentrations of bacterial single-cell protein (Pruteen) dust have complained of "sticky eyes" and influenza-like symptoms. Over four years, surveillance of a work force of 70 men with a programme that included a respiratory health questionnaire, skin prick testing, serum testing for precipitating antibodies, lung function measurements, and chest radiography has shown no evidence of allergic reaction or of exposure-related deterioration in lung function. The symptoms experienced may be attributable to exposure to lipopolysaccharide. The results show that Pruteen can be produced and handled without adverse effects on health, provided that adequate measures are taken to prevent exposure to high concentrations of dust.

Growth energetics in the production of bacterial single cell protein from Methanol

AbstractBacteria grown on methanol exhibit a poor efficiency of energy conservation, which is mainly due to the low P/O ratio of 1 associated with methanol oxidation. Thermodynamic considerations indicate that a P/O ratio of at least 2 is possible for this step in substrate oxidation. This low efficiency of energy conservation is reflected in the yield values on methanol, which are very important in the consideration of biomass production from methanol. Unfortunately in continuous culture there is no obvious way to select for organisms with a greater efficiency of energy conservation.