Improving propionic acid production from a hemicellulosic hydrolysate of sorghum bagasse by means of cell immobilization and sequential batch operation.

Propionic acid (PA) is an important organic compound with extensive application in different industrial sectors and is currently produced by petrochemical processes. The production of PA by large-scale fermentation processes presents a bottleneck, particularly due to low volumetric productivity. In this context, the present work aimed to produce PA by a biochemical route from a hemicellulosic hydrolysate of sorghum bagasse using the strain Propionibacterium acidipropionici CIP 53164. Conditions were optimized to increase volumetric productivity and process efficiency. Initially, in simple batch fermentation, a final concentration of PA of 17.5 g⋅L-1 was obtained. Next, fed batch operation with free cells was adopted to minimize substrate inhibition. Although a higher concentration of PA was achieved (38.0 g⋅L-1 ), the response variables (YP/S = 0.409 g⋅g-1 and QP = 0.198 g⋅L-1 ⋅H-1 ) were close to those of the simple batch experiment. Finally, the fermentability of the hemicellulosic hydrolysate was investigated in a sequential batch with immobilized cells. The PA concentration achieved a maximum of 35.3 g⋅L-1 in the third cycle; moreover, the volumetric productivity was almost sixfold higher (1.17 g⋅L-1 ⋅H-1 ) in sequential batch than in simple batch fermentation. The results are highly promising, providing preliminary data for studies on scaling up the production of this organic acid.

Luteococcus peritonei sp. nov., isolated from the human peritoneum.

An unusual catalase-positive pleomorphic Gram-positive rod isolated from a human clinical specimen was subjected to a polyphasic taxonomic analysis. Comparative 16S rRNA gene sequence analysis revealed the unknown bacterium was a member of the high G+C branch of the Gram-positive bacteria (Actinobacteria), and was phylogenetically a member of the family Propionibacteriaceae, with Luteococcus japonicus as its nearest relative. Based on both phenotypic and phylogenetic evidence, it is proposed that the unknown bacterium be classified in the genus Luteococcus, as Luteococcus peritonei sp. nov. The type strain of Luteococcus peritonei is CCUG 38120T.

Friedmanniella spumicola sp. nov. and Friedmanniella capsulata sp. nov. from activated sludge foam: gram-positive cocci that grow in aggregates of repeating groups of cocci.

Two Gram-positive, non-motile, non-spore-forming, strictly aerobic, pigmented cocci, strains Ben 107T and Ben 108T, growing in aggregates were isolated from activated sludge samples by micromanipulation. Both possessed the rare type A3 gamma' peptidoglycan. Major menaquinones of strain Ben 107T were MK-9(H4) and MK-7(H2), and the main cellular fatty acid was 12-methyltetradecanoic acid (ai-C15:0). In strain Ben 108T, MK-9(H4), MK-9(H2) and MK-7(H4) were the menaquinones and again the main fatty acid was 12-methyltetradecanoic acid (ai-C15:0). Polar lipids in both strains consisted of phosphatidyl inositol, phosphatidyl glycerol and diphosphatidyl glycerol with two other unidentified glycolipids and phospholipids also present in both. These data, together with the 16S rDNA sequence data, suggest that strain Ben 107T belongs to the genus Friedmanniella which presently includes a single recently described species, Friedmanniella antarctica. Although the taxonomic status of strain Ben 108T is far less certain, on the basis of its 16S rRNA sequence it is also adjudged to be best placed in the genus Friedmanniella. The chemotaxonomic characteristics and DNA-DNA hybridization data support the view that Ben 107T and Ben 108T are novel species of the genus Friedmanniella. Hence, it is proposed that strain Ben 107T (= ACM 5121T) is named as Friedmanniella spumicola sp. nov. and strain Ben 108T (= ACM 5120T) as Friedmanniella capsulata sp. nov.