Changes in freshwater sediment microbial populations during fermentation of crude glycerol

BACKGROUND: This work studied how the exposure to an unusual substrate forced a change in microbial populations during anaerobic fermentation of crude glycerol, a by-product of biodiesel production, with freshwater sediment used as an inoculum. RESULTS: The microbial associations almost completely (99.9%) utilized the glycerol contained in crude glycerol 6 g L 1 within four days, releasing gases, organic acids (acetic, butyric) and alcohols (ethanol, n-butanol) under anaerobic conditions. In comparison with control medium without glycerol, adding crude glycerol to the medium increased the amount of ethanol and n-butanol production and it was not significantly affected by incubation temperature (28 C or 37 C), nor incubation time (4 or 8 d), but it resulted in reduced amount of butyric acid. Higher volume of gas was produced at 37 C despite the fact that the overall bacterial count was smaller than the one measured at 20 C. Main microbial phyla of the inoculum were Actinobacteria, Proteobacteria and Firmicutes. During fermentation, significant changes were observed and Firmicutes, especially Clostridium spp., began to dominate, and the number of Actinobacteria and Gammaproteobacteria decreased accordingly. Concentration of Archaea decreased, especially in medium with crude glycerol. These changes were confirmed both by culturing and culture-independent (concentration of 16S rDNA) methods. CONCLUSIONS: Crude glycerol led to the adaptation of freshwater sediment microbial populations to this substrate. Changes of microbial community were a result of a community adaptation to a new source of carbon.

Enhanced pyruvic acid yield in an osmotic stress-resistant mutant of Yarrowia lipolytica

BACKGROUND: Pyruvic acid (PA), a vital α-oxocarboxylic acid, plays an important role in energy and carbon metabolism. The oleaginous yeast Yarrowia lipolytica (Y. lipolytica) has considerable potential for the production of PA. An increased NaCl concentration reportedly increases the biomass and PA yield of Y. lipolytica. RESULTS: To increase the yield of PA, the NaCl-tolerant Y. lipolytica A4 mutant was produced using the atmospheric and room temperature plasma method of mutation. The A4 mutant showed growth on medium containing 160 g/L NaCl. The PA yield of the A4 mutant reached 97.2 g/L at 120 h (0.795 g/g glycerol) in a 20-L fermenter with glycerol as the sole carbon source, which was 28.9% higher than that of the parental strain. CONCLUSION: The PA yield from Y. lipolytica can be improved by increasing its NaCl tolerance.

Free fatty acids reduce metabolic stress and favor a stable production of heterologous proteins in Pichia pastoris

ABSTRACT The growth of yeasts in culture media can be affected by many factors. For example, methanol can be metabolized by other pathways to produce ethanol, which acts as an inhibitor of the heterologous protein production pathway; oxygen concentration can generate aerobic or anaerobic environments and affects the fermentation rate; and temperature affects the central carbon metabolism and stress response protein folding. The main goal of this study was determine the implication of free fatty acids on the production of heterologous proteins in different culture conditions in cultures of Pichia pastoris. We evaluated cell viability using propidium iodide by flow cytometry and thiobarbituric acid reactive substances to measure cell membrane damage. The results indicate that the use of low temperatures and low methanol concentrations favors the decrease in lipid peroxidation in the transition phase from glycerol to methanol. In addition, a temperature of 14 ºC + 1%M provided the most stable viability. By contrast, the temperature of 18 ºC + 1.5%M favored the production of a higher antibody fragment concentration. In summary, these results demonstrate that the decrease in lipid peroxidation is related to an increased production of free fatty acids.

Bioconversion of waste cooking oil glycerol from cabbage extract to lactic acid by Rhizopus microsporus

Abstract Glycerol from spent oil was processed by transesterification for biodiesel production. Although glycerol contains many types of impurities, it can be used as a C-source for lactic acid production by fungi, such as Rhizopus microsporus. In this study, we found that wild type R. microsporus (LTH23) produced more lactic acid than the mutant strains on cabbage glycerol media (CG media). More lactic acid was produced on CG media than on cabbage extract media (C media) by about two-fold in batch fermentation conditions. In addition, we found that lactic acid production in a fed-batch process was also slightly higher than in a batch process. To study the combined effects of pH, urea, and glycerol waste concentration on lactic acid production, a response surface methodology was used. The optimum pH, urea, and glycerol waste concentrations were pH 6.5, 3.75 g/L, and 17 g/L, respectively. The maximum lactic acid production predicted by this equation model was 4.03 g/L.

Co-production of hydrogen and ethanol by Escherichia coli SS1 and its recombinant

Background: The development of a potential single culture that can co-produce hydrogen and ethanol is beneficial for industrial application. Strain improvement via molecular approach was proposed on hydrogen and ethanol co-producing bacterium, Escherichia coli SS1. Thus, the effect of additional copy of native hydrogenase gene hybC on hydrogen and ethanol co-production by E. coli SS1 was investigated. Results: Both E. coli SS1 and the recombinant hybC were subjected to fermentation using 10 g/L of glycerol at initial pH 7.5. Recombinant hybC had about 2-fold higher cell growth, 5.2-fold higher glycerol consumption rate and 3-fold higher ethanol productivity in comparison to wild-type SS1. Nevertheless, wild-type SS1 reported hydrogen yield of 0.57 mol/mol glycerol and ethanol yield of 0.88 mol/mol glycerol, which were 4- and 1.4-fold higher in comparison to recombinant hybC. Glucose fermentation was also conducted for comparison study. The performance of wild-type SS1 and recombinant hybC showed relatively similar results during glucose fermentation. Additional copy of hybC gene could manipulate the glycerol metabolic pathway of E. coli SS1 under slightly alkaline condition. Conclusions: HybC could improve glycerol consumption rate and ethanol productivity of E. coli despite lower hydrogen and ethanol yields. Higher glycerol consumption rate of recombinant hybC could be an advantage for bioconversion of glycerol into biofuels. This study could serve as a useful guidance for dissecting the role of hydrogenase in glycerol metabolism and future development of effective strain for biofuels production.

Evaluation of short-chain-length polyhydroxyalkanoate accumulation in Bacillus aryabhattai

Abstract This study was focused on the polyhydroxybutyrate (PHB) accumulation property of Bacillus aryabhattai isolated from environment. Twenty-four polyhydroxyalkanoate (PHA) producers were screened out from sixty-two environmental bacterial isolates based on Sudan Black B colony staining. Based on their PHA accumulation property, six promising isolates were further screened out. The most productive isolate PHB10 was identified as B. aryabhattai PHB10. The polymer production maxima were 3.264 g/L, 2.181 g/L, 1.47 g/L, 1.742 g/L and 1.786 g/L in glucose, fructose, maltose, starch and glycerol respectively. The bacterial culture reached its stationary and declining phases at 18 h and 21 h respectively and indicated growth-associated PHB production. Nuclear Magnetic Resonance (NMR) spectra confirmed the material as PHB. The material has thermal stability between 30 and 140 °C, melting point at 170 °C and maximum thermal degradation at 287 °C. The molecular weight and poly dispersion index of the polymer were found as 199.7 kDa and 2.67 respectively. The bacterium B. aryabhattai accumulating PHB up to 75% of cell dry mass utilizing various carbon sources is a potential candidate for large scale production of bacterial polyhydroxybutyrate.

Cultivation of Pichia pastoris carrying the scFv anti LDL (-) antibody fragment. Effect of preculture carbon source

Abstract Antibodies and antibody fragments are nowadays among the most important biotechnological products, and Pichia pastoris is one of the most important vectors to produce them as well as other recombinant proteins. The conditions to effectively cultivate a P. pastoris strain previously genetically modified to produce the single-chain variable fragment anti low density lipoprotein (-) under the control of the alcohol oxidase promoter have been investigated in this study. In particular, it was evaluated if, and eventually how, the carbon source (glucose or glycerol) used in the preculture preceding cryopreservation in 20% glycerol influences both cell and antibody fragment productions either in flasks or in bioreactor. Although in flasks the volumetric productivity of the antibody fragment secreted by cells precultured, cryopreserved and reactivated in glycerol was 42.9% higher compared with cells precultured in glucose, the use of glycerol in bioreactor led to a remarkable shortening of the lag phase, thereby increasing it by no less than thrice compared to flasks. These results are quite promising in comparison with those reported in the literature for possible future industrial applications of this cultivation, taking into account that the overall process time was reduced by around 8 h.

Utilization of a waste glycerol fraction using and reusing immobilized Gluconobacter oxydans ATCC 621 cell extract

Background: Depletion of petroleum resources has enforced the search for alternative sources of renewable energy. Introduction of biofuels into the market was expected to become a solution to this disadvantageous situation. Attempts to cover fuel demand have, however, caused another severe problem­the waste glycerol generated during biodiesel production at a concentration of approximately 10% w/w. This, in turn, prompted a global search for effective methods of valorization of the waste fraction of glycerol. Results: Utilization of the waste fraction at 48 h with an initial glycerol concentration of 30 g·L-1 and proceeding with 62% efficiency enabled the production of 9 g·L-1 dihydroxyacetone at 50% substrate consumption. The re-use of the immobilized biocatalyst resulted in a similar concentration of dihydroxyacetone (8.7 g·L-1) in two-fold shorter time, with an efficiency of 85% and lower substrate consumption (35%). Conclusions: The method proposed in this work is based on the conversion of waste glycerol to dihydroxyacetone in a reaction catalyzed by immobilized Gluconobacter oxydans cell extract with glycerol dehydrogenase activity, and it could be an effective way to convert waste glycerol into a valuable product.

Glicerina associada à ureia na terminação de bovinos: parâmetros ruminais, digestibilidade e massa microbiana / Glycerin associated with urea in finishing cattle: ruminal fermentation, digestibility and microbial mass

O objetivo desta pesquisa foi verificar a combinação de glicerina com ureia, quanto aos parâmetros ruminais, à digestibilidade e à qualidade da massa microbiana. O trabalho foi conduzido na Unidade Animal de Estudos Digestivos e Metabólicos, pertencente à Faculdade de Ciências Agrárias e Veterinárias-FCAV/Unesp, Câmpus de Jaboticabal. Seis animais da raça Nelore providos de cânulas ruminais foram utilizados para verificar os parâmetros pH, nitrogênio amoniacal, a digestibilidade e a massa microbiana, distribuídos em quadrado latino 6x6. Seis dietas com energia metabolizável e proteína bruta semelhantes foram formuladas, utilizando-se a proporção volumoso:concentrado de 30:70. O volumoso utilizado foi silagem de milho. Os concentrados utilizados foram compostos por milho, casca de soja, farelo de girassol, glicerina e ureia. Os tratamentos foram: C = controle; U = 1% de ureia; G10 = 10% de glicerina; GU10 = 1% de ureia e 10% de glicerina, G20 = 20% de glicerina e GU20 = 20% de glicerina e 1% de ureia. Houve influência das dietas no crescimento dos microrganismos ruminais, no pH e no nitrogênio amoniacal. Dietas com 20% de glicerina na matéria seca da dieta diminuem a população de protozoários ruminais. A inclusão de glicerina diminui a digestibilidade de componentes fibrosos da dieta.(AU)

The aim of this research was to investigate the combination of glycerol with urea as the ruminal parameters, digestibility and quality of microbial mass. The work was conducted at the Animal Unit of Digestive and Metabolic Studies belonging to the Faculty of Agricultural Sciences and Veterinárias-FCAV/Unesp campus Jaboticabal. Six animals fitted with rumen cannulas Nellore were used to verify the parameters pH, ammonia nitrogen, digestibility, and microbial mass distributed in a 6x6 Latin square. Six diets with similar metabolizable energy and crude protein were formulated using the forage:concentrate ratio of 30:70. The roughage used was corn silage. The concentrates used were composed of corn, soybean hulls, sunflower meal, glycerin and urea. The treatments were: C = control, U = 1 % urea, G10 = 10 % glycerin, GU10 = 1 % urea and 10 % glycerol, G20 = 20 % glycerin and GU20 = 20 % glycerin and 1 % urea. Diets with glycerin had lower digestibility of NDF and hemicellulose. There was no influence of diets on the growth of rumen microorganisms, pH and ammonia nitrogen. Diets with 20 % glycerin in the diet dry matter decrease the population of rumen protozoa. The addition of glycerol decreases the digestibility of fibrous components of the diet.(AU)

Effects of oxygen transfer coefficient on dihydroxyacetone production from crude glycerol

Abstract The principal objective of this study was to evaluate the kinetics of dihydroxyacetone production by Gluconobacter frateurii CGMCC 5397 under different oxygen volumetric mass transfer coefficient (kLa) conditions in submerged bioreactors using biodiesel-derived crude glycerol as the carbon source. kLa is a key fermentation parameter for the production of dihydroxyacetone. Cultivations were conducted in baffled- and unbaffled-flask cultures (the kLa values were 24.32 h−1 and 52.05 h−1, respectively) and fed-batch cultures (the kLa values were held at 18.21 h−1, 46.03 h−1, and 82.14 h−1) to achieve high dihydroxyacetone concentration and productivity. The results showed that a high kLa could dramatically increase dihydroxyacetone concentrations and productivities. The baffled-flask culture (with a kLa of 52.05 h−1) favored glycerol utilization and dihydroxyacetone production, and a dihydroxyacetone concentration as high as 131.16 g/L was achieved. When the kLa was set to 82.14 h−1 in the fed-batch culture, the dihydroxyacetone concentration, productivity and yield were 175.44 g/L, 7.96 g/L/h and 0.89 g/g, respectively, all of which were significantly higher than those in previous studies and will benefit dihydroxyacetone industrial production.

Renin-angiotensin system blockers regulate the metabolism of isolated fat cells in vitro

Due to the presence of the renin-angiotensin system (RAS) in tissues and its specific influence on white adipose tissue, fat cells are possible targets of pharmacological RAS blockers commonly used as anti-hypertensive drugs. In the present study, we investigated the effects of different RAS blockers on fat cell metabolism, more specifically on lipolysis, lipogenesis and oxidation of energy substrates. Isolated primary adipocytes were incubated with different RAS blockers (aliskiren, captopril and losartan) in vitro for 24 h and lipolysis, lipogenesis and glucose oxidation capacities were determined in dose-response assays to a β-adrenergic agonist and to insulin. Although no change was found in lipolytic capacity, the RAS blockers modulated lipogenesis and glucose oxidation in a different way. While captopril decreased insulin-stimulated lipogenesis (−19% of maximal response and −60% of insulin responsiveness) due to reduced glucose derived glycerol synthesis (−19% of maximal response and 64% of insulin responsiveness), aliskiren increased insulin-stimulated glucose oxidation (+49% of maximal response and +292% of insulin responsiveness) in fat cells. Our experiments demonstrate that RAS blockers can differentially induce metabolic alterations in adipocyte metabolism, characterized by a reduction in lipogenic responsiveness or an increase in glucose oxidation. The impact of RAS blockers on adipocyte metabolism may have beneficial implications on metabolic disorders during their therapeutic use in hypertensive patients.

The effect of high concentrations of glycerol on the growth, metabolism and adaptation capacity of Clostridium butyricum DSP1

Background The production of biofuels from renewable energy sources is one of the most important issues in biotechnology today. The process is known to generate various by-products, for example glycerol that is obtained in the making of biodiesel from rapeseed oil. Crude glycerol may be utilized in many ways, including microbial conversion to 1,3-propanediol. The main drawback of that technology is the use of high concentrations of glycerol, which inhibits the growth of bacterial cells. Results This study investigated the impact of crude glycerol on Clostridium butyricum DSP1 and its ability to adapt to an environment of high osmotic pressure. It was found that a crude glycerol concentration of up to 70 g/L did not have an inhibitory effect on C. butyricum DSP1. Adaptation procedures involving the passage of metabolically active biomass from a fermentation medium with a lower concentration of crude glycerol to one with a greater substrate concentration allowed breaking the barrier of high osmotic pressure (150 g/L crude glycerol) and receiving a 1,3-PD concentration of 74 g/L in a batch culture operation. The work looked into intracellular modifications shown by proteomic profiling in order to explain the mechanisms underlying the response and adaptation of bacterial cells exposed to unfavorable environmental conditions. Conclusions This study of the effect of glycerol on the growth and metabolism of C. butyricum DSP1 demonstrated that the maximum substrate concentrations that do not inhibit the metabolic activity of bacterial cells are 90 g/L and 70 g/L for pure and crude glycerol, respectively.

1, 3-Propanediol production from crude glycerol by Clostridium butyricum DSP1 in repeated batch

Background The production of biofuels from renewable energy sources is one of the most important issues in industrial biotechnology today. The process is known to generate various by-products, for example crude glycerol, which is obtained in the making of biodiesel from rapeseed oil. Crude glycerol may be utilized in many ways, including microbial conversion to 1,3-propanediol (1,3-PD), a raw material for the synthesis of polyesters and polyurethanes. Results The paper presents results of a study on the synthesis of 1,3-propanediol from crude glycerol by a repeated batch method with the use of Clostridium butyricum DSP1. Three cycles of fermentation medium replacement were carried out. The final concentration of 1,3-PD was 62 g/L and the maximum productivity, obtained during the second cycle, reached 1.68 g/L/h. Additionally, experiments conducted in parallel to the above involved using the entire quantity of the culture broth removed from the bioreactor to inoculate successive portions of fermentation media containing crude glycerol at concentrations of 80 g/L and 100 g/L. Under those conditions, the maximum 1,3-PD concentrations were 43.2 g/L and 54.2 g/L. Conclusions The experiments proved that by using a portion of metabolically active biomass as inoculum for another fermentation formula it is possible to eliminate the stage of inoculum growth and thereby reduce the length of the whole operation. Additionally, that strategy avoids the phase of microbial adaptation to a different source of carbon such as crude glycerol, which is more difficult to utilize, thus improving the kinetic parameters of 1,3-PD production.

Biotechnological potential of Clostridium butyricum bacteria

In response to demand from industry for microorganisms with auspicious biotechnological potential, a worldwide interest has developed in bacteria and fungi isolation. Microorganisms of interesting metabolic properties include non-pathogenic bacteria of the genus Clostridium, particularly C. acetobutylicum, C. butyricum and C. pasteurianum. A well-known property of C. butyricum is their ability to produce butyric acid, as well as effectively convert glycerol to 1,3-propanediol (38.2 g/L). A conversion rate of 0.66 mol 1,3-propanediol/mol of glycerol has been obtained. Results of the studies described in the present paper broaden our knowledge of characteristic features of C. butyricum specific isolates in terms of their phylogenetic affiliation, fermentation capacity and antibacterial properties.

Impact of water potential on growth and germination of Fusarium solani soilborne pathogen of peanut

Studies were conducted to determine the effect of osmotic and matric stress on germination and growth of two Fusarium solani strains, the etiological agent responsible of peanut brown root rot. Both strains had similar osmotic and matric potential ranges that allowed growth, being the latter one narrower. F. solani showed the ability to grow down to -14 MPa at 25 °C in non-ionic modified osmotic medium, while under matric stress this was limited to -8.4 MPa at 25 °C. However, both strains were seen to respond differently to decreasing osmotic and matric potentials, during early stages of germination. One strain (RC 338) showed to be more sensitive to matric than osmotic (non ionic) and the other one (RC 386) showed to be more sensitive to osmotic than matric imposed water stress. After 24 h of incubation, both isolates behaved similarly. The minimum water potential for germination was -8.4 MPa on glycerol amended media and -5.6 MPa for NaCl and PEG amended media, respectively. The knowledge of the water potential range which allow mycelia growth and spore germination of F. solani provides an inside to the likely behaviour of this devastating soilborne plant pathogen in nature and has important practical implications.

Volatile fatty acids influence on the structure of microbial communities producing PHAs

Polyhydroxyalkanoates (PHAs) can be produced by microorganisms and are a biodegradable alternative to fossil-fuel based plastics. Currently, the focus is on reducing production costs by exploring alternative substrates for PHAs production, and on producing copolymers which are less brittle than monomers. Accordingly, this study used a substrate consisting of wastewater from waste-glycerol fermentation, supplemented with different amounts of acetic and propionic acids. These substrates were used to feed mixed microbial communities enriched from activated sludge in a sequencing batch reactor. A reactor supplemented with 2 mL of acetic acid produced 227.8 mg/L of a homopolymer of hydroxybutyrate (3HB); 4 mL of acetic acid produced 279.8 mg/L 3HB; whereas 4 mL of propionic acid produced 673.0 mg/L of a copolymer of 3HB and 3HV (hydroxyvalerate). Ribosomal Intergenic Spacer Analysis (RISA) was used to show the differences between the communities created in the reactors. Thauera species predominated in biomass that produced 3HB; Paracoccus denitrificans in the biomass that produced 3HB-co-3HV. Because P. denitrificans produced the more desirable copolymer, it may be advantageous to promote its growth in PHAs-producing reactors by adding propionate.

An increasing of the efficiency of microbiological synthesis of 1, 3-propanediol from crude glycerol by the concentration of biomass

Background 1,3-Propanodiol (1,3-PD), is used in the production of polytrimethylene terephthalate (PTT), an aromatic polyester that exhibits high elastic recoveries. It is also employed as a supplement with low solidification properties, a solvent and a lubricant in the formof propylene glycol. 1,3-PD is effectively synthesized by a microbiological way from crude glycerol. The main problem of this technology is using a high concentration of glycerol, which is a limiting factor for bacteria cells growth (especially in batch fermentation). Results In this work, the influence of different glycerol concentration in batch fermentation on Clostridium butyricum DSP1 metabolism was investigated. The biomass was concentrated for two times with the use of membrane module (in case of increasing kinetic parameters). Increased optical density of bacteria cells six times increased the productivity of 1,3-PD in cultivation with 20 g/L of glycerol at the beginning of the process, and more than two times in cultivation with 60-80 g/L. Also the possibility of complete attenuation of 140 g/L of crude glycerol in the batch fermentation was investigated. During the cultivation, changes of protein profiles were analyzed. The most significant changes were observed in the cultivation in the medium supplemented with 80 g/L of glycerol. They related mainly to the DNA protein reconstructive systems, protective proteins (HSP), and also the enzymatic catalysts connected with glycerol metabolic pathway. Conclusions The application of filtration module in batch fermentation of crude glycerol by C. butyricum DSP1 significantly increased the productivity of the process.

Evaluation of stress tolerance and fermentative behavior of indigenous Saccharomyces cerevisiae

Sixty six indigenous Saccharomyces cerevisiae strains were evaluated in stressful conditions (temperature, osmolarity, sulphite and ethanol tolerance) and also ability to flocculate. Eighteen strains showed tolerant characteristics to these stressful conditions, growing at 42 ºC, in 0.04% sulphite, 1 mol L-1 NaCl and 12% ethanol. No flocculent characteristics were observed. These strains were evaluated according to their fermentative performance in sugar cane juice. The conversion factors of substrates into ethanol (Yp/s), glycerol (Yg/s) and acetic acid (Yac/s), were calculated. The highest values of Yp/s in sugar cane juice fermentation were obtained by four strains, one isolated from fruit (0.46) and the others from sugar cane (0.45, 0.44 and 0.43). These values were higher than the value obtained using traditional yeast (0.38) currently employed in the Brazilian bioethanol industry. The parameters Yg/s and Yac/s were low for all strains. The UFLA FW221 presented the higher values for parameter related to bioethanol production. Thus, it was tested in co-culture with Lactobacillus fermentum. Besides this, a 20-L vessel for five consecutive batches of fermentation was performed. This strain was genetically stable and remained viable during all batches, producing high amounts of ethanol. The UFLA FW221 isolated from fruit was suitable to produce bioethanol in sugar cane juice. Therefore, the study of the biodiversity of yeasts from different environmental can reveal strains with desired characteristics to industrial applications.

Evaluating Colombian Clostridium spp. Strains hydrogen production using glycerol as substrate

Background: The ability for hydrogen production of 13 native strains of Clostridium spp. strains isolated from Colombian soil was evaluated using glycerol substrate. Glycerol to hydrogen conversion was investigated using a batch fermentation reactor and industrial glycerol source (50 g.l-1, pH 7.00). Results: The results were quantified regarding acids, hydrogen, biomass and solvent production. The selected strain gave good hydrogen over production output at 14.4 mmol H2.l-1, productivity 0.3167 mg H2.h-1 l-1 culture mediumand yield 0.1962 mol H2.mol-1 glycerol. A further fermentation assay a 4.0 liter batch reactor let to being 0.26 mg.l-1.h-1 after 18 hrs of fermentation. Logistic model, Luedeking-Piret model and Luedeking-Piret modified models were used for modeling changes in cell growth, hydrogen production and substrate consumption (Correlation coefficients R² = 0.95 for biomass substrate, R² = 0.77 hydrogen production). Conclusions: Our results indicate that hydrogen production through glycerol bioconversion by native strains is possible.

Glicerina semipurificada vegetal e mista na alimentação de coelhos em crescimento / Vegetal and mixed semipurified glycerin in the feeding of growing rabbits

Dois experimentos foram conduzidos com o objetivo de determinar a energia digestível da glicerina semipurificada vegetal e mista e o desempenho de coelhos em crescimento alimentados com dietas contendo os coprodutos. No ensaio de digestibilidade, foram utilizados 108 coelhos da raça Nova Zelândia Branco, com 45 dias de idade, distribuídos ao acaso em nove tratamentos (0, 4, 8, 12 e 16% de inclusão de glicerina vegetal e mista na dieta), com 12 repetições. Para o ensaio de desempenho, utilizaram-se 180 coelhos da raça Nova Zelândia Branco, dos 32 aos 70 dias de idade, distribuídos ao acaso em arranjo fatorial 2 x 4 (dois tipos de glicerina e quatro porcentagens de inclusão: 3, 6, 9 e 12%) mais uma dieta referência, com 10 repetições e dois animais por unidade experimental. Glicerinas vegetal e mista apresentaram energia digestível de 4.048 e 3.697kcal/kg MS, respectivamente. Entre 32 e 50 dias de idade dos coelhos, a dieta com 12% de glicerina mista prejudicou (P<0,05) o ganho de peso (32,14 g/dia), a conversão alimentar (3,57) e o custo por quilo de ganho de peso (R$ 2,08) em relação à dieta referência (39,42g/dia, 2,87 e R$1,69, respectivamente). Dos 32 aos 70 dias, o ganho de peso (30,11g/dia) e a conversão alimentar (3,99) dos animais que receberam 12% de glicerina mista na dieta foram piores (P<0,05) em relação aos da dieta referência (34,00g/dia e 3,65, respectivamente). Para as características de desempenho, dos 32 aos 70 dias, não foram verificadas diferenças (P>0,05) entre a inclusão de glicerina vegetal na dieta e a dieta referência, porém a maior viabilidade econômica (P<0,05) foi com 12% de inclusão (R$1,89 x R$2,15, respectivamente). A glicerina vegetal pode ser incluída em até 12% da dieta e a mista, em até 9%, diminuindo o custo de produção sem afetar o desempenho animal.

Two trials were conducted with the goal of determining the digestible energy of vegetal and mixed semi purified glycerin and the performance of growing rabbits fed with diets containing the byproducts. In the digestibility assay 108 New Zealand White rabbits, 45 days old, were used, assigned in a completely randomized design into nine treatments (0, 4, 8, 12 and 16% of glycerins inclusion), with 12 replications. The treatment with 0% of glycerin inclusion was considered the reference diet. In the performance assay, 180 New Zealand White rabbits, 32 to 70 days of age, were assigned to a completely randomized design into a 2 × 4 factorial arrangement (two types of glycerin and four percentages of inclusion: 3, 6, 9 and 12%) plus a reference diet and ten replications with two animals per experimental unit. Vegetal and mixed glycerin showed a digestible energy of 4,048 and 3,697 kcal/kg of dry matter, respectively. From 32 to 50 days of age, the diet with 12% of mixed glycerin affected (P<0.05) weight gain (32.14g/day), feed conversion (3.57) and cost per kilo of weight gain (R$2.08) in relation to the reference diet (39.42g/day, 2.87 and R$ 1.69, respectively). From 32 to 70 days, weight gain (30.11g/day) and feed conversion (3.99) of the animals fed with the diet containing 12% of mixed glycerin were worst (P<0.05) in relation to the reference diet (34.00 g/day and 3.65, respectively). Regarding characteristics of animal performance, from 32 to 70 days, no differences (P>0.05) were observed between the inclusion of vegetal glycerin in the diet and the reference diet, but better economic viability was verified (P<0.05) with the diet containing 12% of vegetal glycerin (R$1.89 x R$2.15, respectively). Vegetal glycerin can be included up to 12% in the diet and mixed up to 9%, reducing production cost without affecting animal performance.