The aim of the present study was to investigate the taxonomic identity of yeasts isolated from the Antarctic continent and to evaluate their ability to produce enzymes (lipase, protease and xylanase) at low and moderate temperatures. A total of 97 yeast strains were recovered from marine and terrestrial samples collected in the Antarctica. The highest amount of yeast strains was obtained from marine sediments, followed by lichens, ornithogenic soils, sea stars, Salpa sp., algae, sea urchin, sea squirt, stone with lichens, Nacella concinna, sea sponge, sea isopod and sea snail. Data from polyphasic taxonomy revealed the presence of 21 yeast species, distributed in the phylum Ascomycota (n = 8) and Basidiomycota (n = 13). Representatives of encapsulated yeasts, belonging to genera Rhodotorula and Cryptococcus were recovered from 7 different Antarctic samples. Moreover, Candida glaebosa, Cryptococcus victoriae, Meyerozyma (Pichia) guilliermondii, Rhodotorula mucilaginosa and R. laryngis were the most abundant yeast species recovered. This is the first report of the occurrence of some species of yeasts recovered from Antarctic marine invertebrates. Additionally, results from enzymes production at low/moderate temperatures revealed that the Antarctic environment contains metabolically diverse cultivable yeasts, which could be considered as a target for biotechnological applications. Among the evaluated yeasts in the present study 46.39, 37.11 and 14.43 % were able to produce lipase (at 15 °C), xylanase (at 15 °C) and protease (at 25 °C), respectively. The majority of lipolytic, proteolytic and xylanolytic strains were distributed in the phylum Basidiomycota and were mainly recovered from sea stars, lichens, sea urchin and marine sediments.

No abstract

Microorganisms from extreme and restrictive eco systems, such as the Antarctic continent, are of great interest due to their ability to synthesize products of commercial value. Among these, enzymes from psychrotolerant and psychrophilic microorganisms offer potential economical benefits due to their high activity at low and moderate temperatures. The cold adapted yeast Rhodotorula mucilaginosa L7 was selected out of 97 yeasts isolated from Antarctica as having the highest extracellular proteolytic activity in preliminary tests. The present study was aimed at evaluating the effects of nutrient composition (peptone, rice bran extract, ammonium sulfate, sodium chloride) and physicochemical parameters (temperature and pH) on its proteolytic activity. A 2 fractional factorial design experiment followed by a central composite design (CCD 2) was performed to optimize the culture conditions and improve the extracellular proteolytic activity. The results indicated that the presence of peptone in the medium was the most influential factor in protease production. Enzymatic activity was enhanced by the interaction between low glucose and peptone concentrations. The optimization of culture conditions with the aid of mathematical modeling enabled a c. 45% increase in proteolytic activity and at the same time reduced the amount of glucose and peptone required for the culture. Thus culture conditions established in this work may be employed in the biotechnological production of this protease.

RESUMO:A busca por matérias primas renováveis e de baixo custo para a obtenção de diferentes insumos é crescente nos últimos tempos, principalmente devido ao fato de possibilitar a redução de custo de produtos alimentícios com alto valor nutritivo.O farelo de arroz com sua riqueza em nutrientes, principalmente como fonte de vitaminas e minerais é um subproduto da agroindústria brasileira com potencial para ser aproveitado na formulação de alimentos. Entretanto, o aproveitamento biotecnológico do farelo de arroz abre perspectivas econômicas de maior valor agregado para sua utilização em diferentes segmentos industriais. Neste trabalho são apresentadas considerações sobre as características e aplicações do farelo de arroz, bem como resultados de pesquisas sobre a sua utilização na suplementação de meios microbiológicos.Palavras-chave: Farelo de arroz. Agroindústria. Subproduto. Bioprocessos. SUMMARY:The search for renewable and low cost raw materials in order to obtain distinct inputs has been increasing, mainly due possibilities of reducing the cost of foods with high nutritious value. Rice bran richness in nutrients, mainly as a source of vitamins and minerals, is a Brazilian agro industrial by-product with potential to be used in food composition. However, the biotechnological use of said rice bran opens economical perspectives of greater collected value due to its use in several different industrial segments. The following work presents comments on the characteristics and applications of rice bran as well as researches results about its uses in the supplementation of microbiological media.Keywords: Rice bran. Agro industrial. By-product. Bioprocesses. INTRODUÇÃO Farelo de arroz: subproduto do beneficiamento do arrozO arroz é considerado o cultivo alimentar de maior importância para muitos países em desenvolvimento e como alimento básico para cerca de 2,4 bilhões de pessoas no mundo, atinge na Ásia, uma produção e consumo da ordem de 90% (EMBRAPA, 2004). Segundo estudo realizado pela FIESP com o apoio do Ministério da Agricultura, o Brasil se destaca como o maior produtor fora do continente asiático e está entre os dez principais produtores mundiais de arroz, o

Oat hull hemicellulosic hydrolysate obtained by diluted acid hydrolysis was employed as fermentation medium for Pichia stipitis cultivation. A comparison between the use of treated hydrolysate with 1% activated charcoal to reduce the toxic compounds generated during the hydrolysis process and untreated hydrolysate as a control was conducted. In the cultures using treated hydrolysate the total consumption of glucose, low xylose consumption and ethanol and glycerol formation were observed. The medium formulated with untreated hydrolysate showed morphological cell modifications with consequently cell death, no ethanol formation and formation of glycerol as byproduct of fermentative process, probably as a response to stressful conditions to yeast due to presence of high concentration of toxic compounds. Thus, further studies are suggested in order to determine the best conditions for hydrolysis and detoxification of the hydrolysate to improve the fermentative performance of P. stipitis