Microbial lipid production: screening with yeasts grown on Brazilian molasses.

Rhodotorula glutinis CCT 2182, Rhodosporidium toruloides CCT 0783, Rhodotorula minuta CCT 1751 and Lipomyces starkeyi DSM 70296 were evaluated for the conversion of sugars from Brazilian molasses into single-cell oil (SCO) feedstock for biodiesel. Pulsed fed-batch fermentations were performed in 1.65 l working volume bioreactors. The maximum specific growth rate (µmax), lipid productivity (Pr) and cellular lipid content were, respectively, 0.23 h(-1), 0.41 g l(-1) h(-1), and 41% for Rsp. toruloides; 0.20 h(-1), 0.27 g l(-1) h(-1), and 36% for Rta. glutinis; 0.115 h(-1), 0.135 g l(-1) h(-1), and 27 % for Rta. minuta; and 0.11 h(-1), 0.13 g l(-1) h(-1), and 32% for L. starkeyi. Based on their microbial lipid productivity, content, and profile, Rsp. toruloides and Rta. glutinis are promising candidates for biodiesel production from Brazilian molasses. All the oils from the yeasts were similar to the composition of plant oils (rapeseed and soybean) and could be used as raw material for biofuels, as well as in food and nutraceutical products.

PHA(MCL) biosynthesis systems in Pseudomonas aeruginosa and Pseudomonas putida strains show differences on monomer specificities.

The production of PHA from plant oils by Pseudomonas species soil isolated from a sugarcane crop was evaluated. Out of 22 bacterial strains three were able to use efficiently plant oils to grow and to accumulate PHA. Pseudomonas putida and Pseudomonas aeruginosa strains produced PHA presenting differences on monomer composition compatible with variability on monomer specificity of their PHA biosynthesis system. The molar fraction of 3-hydroxydodecanoate detected in the PHA was linearly correlated to the oleic acid supplied. A non-linear relationship between the molar fractions of 3-hydroxy-6-dodecenoate (3HDdDelta(6)) detected in PHA and the linoleic acid supplied was observed, compatible with saturation in the biosynthesis system capability to channel intermediate of beta-oxidation to PHA synthesis. Although P. putida showed a higher 3HDdDelta(6) yield from linoleic acid when compared to P. aeruginosa, in both species it was less than 10% of the maximum theoretical value. These results contribute to the knowledge about the biosynthesis of PHA with a controlled composition from plant oils allowing in the future establishing the production of these polyesters as tailor-made polymers.

Poly-3-hydroxybutyrate (P3HB) production by bacteria from xylose, glucose and sugarcane bagasse hydrolysate.

Fifty-five bacterial strains isolated from soil were screened for efficient poly-3-hydroxybutyrate (P3HB) biosynthesis from xylose. Three strains were also evaluated for the utilization of bagasse hydrolysate after different detoxification steps. The results showed that activated charcoal treatment is pivotal to the production of a hydrolysate easy to assimilate. Burkholderia cepacia IPT 048 and B. sacchari IPT 101 were selected for bioreactor studies, in which higher polymer contents and yields from the carbon source were observed with bagasse hydrolysate, compared with the use of analytical grade carbon sources. Polymer contents and yields, respectively, reached 62% and 0.39 g g(-1) with strain IPT 101 and 53% and 0.29 g g(-1) with strain IPT 048. A higher polymer content and yield from the carbon source was observed under P limitation, compared with N limitation, for strain IPT 101. IPT 048 showed similar performances in the presence of either growth-limiting nutrient. In high-cell-density cultures using xylose plus glucose under P limitation, both strains reached about 60 g l(-1) dry biomass, containing 60% P3HB. Polymer productivity and yield from this carbon source reached 0.47 g l(-1) h(-1) and 0.22 g g(-1), respectively.