In the production of polyhydroxyalkanoates (PHA), the costs of the process are mainly associated with the carbon source and most of the production studies are carried out with commercial strains. In this study, PHA production was evaluated using a strain, SB-34, compared with a referenced strain, Ralstonia eutropha H16, growing in cassava flour hydrolysates as an alternative carbon source. SB-34 reached a biomass maximum of 5,49 ± 0,21 g / L, and PHA product of 3,23 ± 0,21 g / L exceeding the maximum values obtained by R. eutropha H16 (3,8 ± 0,45 g / L and 2,42 ± 0,23 g / L, respectively). Analyzes with FTIR indicate that the polymer obtained with SB-34 is like polyhydroxybutyrate P(3-HB) type. Molecular analysis identified SB-34 as Burkholderia sp. with 96 % of similarity.

El objetivo de este trabajo fue encontrar las condiciones óptimas de hidrólisis enzimática de la cascarilla de arroz pretratada con hidróxido de sodio en autoclave a 121° C. Se evaluaron las variables: FPU/ g sustrato, pH, agitación, tiempo, temperatura y concentración de surfactante mediante un diseño de cribado, resultando estadísticamente significativas todas las variables. Seguidamente se aplicó un diseño de optimización para las variables: pH, FPU y tiempo, descartando las de menor nivel de significación. Finalmente, las mejores condiciones encontradas en los diseños anteriores fueron (pH 5.0, 13 h, y 30 FPU / g de sustrato) posteriormente se aplicaron estas condiciones en experiencias para evaluar la influencia del aumento de celulosa hidrolizable, usando 6%; 8% y 10% de celulosa disponible con rendimientos de sacarificación de 74%, 42% y 16%.

Polyhydroxyalkanoates (PHA) are synthesised by bacteria as carbon storage material. The protein PhaG directs carbon from non-related carbon sources such as glycerol, metabolised through fatty acid de novo synthesis (FAS) pathway, with PHA synthesis. The gene that codifies for this protein has not yet been found in the genome of Ralstonia eutropha H16, a model organism. By bioinformatic comparison to already known PhaG proteins, a PhaG-like protein was found codified by gene H16_A0147 and presence of the gene was preliminary confirmed by PCR. This is the first study that shows the presence and characteristics of a PhaG-like protein in R. eutropha H16 and represents the first step for the identification of a connection between FAS and PHA pathways in this model bacterium. Further gene deletion and enzymatic activity studies are necessary to confirm this potential relationship, which could improve industrial PHA production and utilisation of agro-industrial residues such as glycerol.

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The present study was conducted to evaluate the cellulose production by Gluconacetobacter kakiaceti GM5 by means of two aerobic treatments: the static discontinuous fermentation process (treatment 1) and the discontinuous fermentation process in a rotary shaker (treatment 2). All these experiments were carried out using vinasse as experimental culture media (VM) and were compared with standard media containing glucose at 2% (standard medium (SM)). A sample of each treatment was extracted every 24 h over a period of 168 h. The maximum rates of cellulose produced in treatment 1 using SM added up to 3.63 ± 0.18 g l(-1), and to 4.15 ± 0.16 g l(-1) when VM was used. The amount of cellulose produced in treatment 2 using SM was 2.95 ± 0.09 g l(-1) (which suggests an increase of 37%), and added up to 1.84 ± 0.07 g l(-1) when using VM. A better global yield of both treatments in terms of sugar consumption after 168 h was obtained when using VM: 32% in treatment 1, whereas in treatment 2 it was 9%. A 20% decrease on vinasse COD (Chemical Oxygen Demand) values was found to be yet another important advantage of working with this strain.