Ribonuclease production by Aspergillus species

Ribonuclease production by Aspergillus flavipes. A sulphureus and A. fischeri in semisynthetic medium, after 24-144 hours at 30 degrees C under shaking, was studied. After cultivation, the medium was separated from micelia by filtration and the resultant solution was used as enzymatic extract. The highest amount of biomass and RNase was obtained after 96 hours of cultivation. The enzymes produced by three species presented similar characteristics, with optimum temperature at 55 degrees C and two peaks of activity at pH 4.5 and 7.0. A. flavipes RNases were more sensitive to temperature: 50% of the initial activity was lost after 1 hour at 70 degrees C. After this heat treatment, RNase of A. sulphureus lost 30% of this activity and that of A. fischeri only 16%. The nucleotides released by enzimatic hydrolysis of RNA were separated by ion exchange chromatography in a AG-1X8-formiate column and identified by paper chromatography. This procedure indicated that the raw enzymatic extract of Aspergillus flavipes is able to hydrolyze RNA, releasing 3'-nucleotides monophosphate at pH 4.5 and 3' and 5'-nucleotides monophosphate at pH 7.0 and 8.5. This result suggests that this strain produces two different types of RNase, one acidic and other alcaline, with different specificities

MICROBIAL COUNTS OF DARK RED LATOSOL SAMPLES STORED AT DIFFERENT TEMPERATURES

The number of colony forming units (CFU) of different groups of bacteria and fungi in samples stored at temperatures of 5 to -12oC for 0-32 weeks was evaluated. The number of CFU obtained after the different periods of storage of red latossol soil was compared with the number of colonies obtained immediately after removal of soil samples (time zero). The number of total bacteria and actinomycetes in the samples remained practically unchanged throughout the storage period. The number of Gram-negative bacteria decreased by as much as 69% compared to control, while the number of Bacillus spp and of fungi increased 1.9 to 4.9 times starting from the 12th week in samples stored at 5oC. Except for the variations observed in fungal counts, the remaining groups of bacteria practically showed the same variation in number of colonies in soil samples stored at 5oC and -12oC

Growth of Pediococcus acidilactici on sugar cane blackstrap molasses

Pediococcus acidilactici (IL01) has grown in MRS (Man, Rogosa and Sharpe) broth modified by substitution of glucose by 2.0% (MRS-2), 3.0% (MRS-3), 4.0% (MRS-4) and 5.0% (MRS-5) sugar cane blackstrap molasses. The highest acid production was obtained in MRS-5 broth maintained at a constant pH of 5.0. The highest biomass production was obtained when P. acidilactici was grown in MRS-5 broth at initial pH 6.5, while productivity was higher in MRS-2 broth (28.16%). When the MRS-2 broth was utilized at initial pH 6.5 for a 20-hour fermentation period, the highest growth rate (dx/dt) was found in a period of 8 to 16 hours (0.290 g cells/L.h), while the specific growth rate (µ) was 0.175 (h-1) for that period, differently from the 0.441 (h-1) obtained for the period comprising the 4th to the 12th hour. The growth in MRS broth was 5.08% (2.95 g/l) higher than in MRS-2 broth (2.80 g/l). The data obtained have shown that P. acidilactici has had a significant growth in molasses as the main carbon source, and that it is possible to substitute MRS glucose by this carbon source with the purpose of obtaining a more economical growth medium for the potential large scale productions.<br>Pediococcus acidilactici (IL01) cresceu em caldo MRS (Man, Rogosa and Sharpe) modificado por adição de 2,0% (MRS-2), 3,0% (MRS-3), 4,0% (MRS-4) and 5,0% (MRS-5) de melaço de cana de açúcar, em substituição à glicose. A maior produção de ácido ocorreu em caldo MRS-5 com pH constante 5,0. A produção de biomassa foi mais acentuada em caldo MRS-5 com pH inicial de 6,5, embora a produtividade tenha sido maior em caldo MRS-2 (28,16%). Em caldo MRS-2 e em pH inicial de 6,5 durante uma fermentação de 20 horas, a velocidade de crescimento (dx/dt) foi maior entre a 8ª e 16ª hora (0,290 g celulas/L.h) enquanto a velocidade específica de crescimento µ foi 0,175 (h-1) para este período, diferente de 0,441 (h-1) obtido no período compreendido entre a 4ª e 12ª hora. O crescimento em caldo MRS foi 5,08% (2,95 g/l) maior que em caldo MRS-2 (2,80 g/l). Os dados obtidos mostraram que P. acidilactici cresceu bem em melaço como principal fonte de carbono e que é possível substituir a glicose do MRS por esta fonte de carbono, com o objetivo de obter um meio de crescimento mais econômico para eventuais produções em grande escala

EVALUATION OF THE VIABILITY OF PLEUROTUS SPP. STRAINS AFTER LIQUID NITROGEN CRYOPRESERVATION

Viability of 6 mushroom strains of the Pleurotus genus (2 from P. djamor var. djamor, 1 from P. ostreatus var. ostreatus, 2 from P. ostreatus var. columbinus and 1 from P. pulmonarius) after liquid nitrogen cryopreservation (-196º) was evaluated. The contact time for the mycelia of these strains with the cryoprotectant (glycerol) was studied 1, 2 and 3 hours before freezing. We also tested the effect of different times (5, 10 and 15 minutes) and temperatures (30, 45 and 60ºC) of the thawing system for mycelial recovery. The results showed a marked tendency toward faster mycelial recovery when samples were thawed at 30ºC, while at 60ºC no recovery was observed. A change in thawing and contact times with the cryoprotectant did not affect the results significantly, as the thawing temperature and strain employed affected

MICROBIAL COUNTS OF DARK RED LATOSOL SAMPLES STORED AT DIFFERENT TEMPERATURES

The number of colony forming units (CFU) of different groups of bacteria and fungi in samples stored at temperatures of 5 to -12oC for 0-32 weeks was evaluated. The number of CFU obtained after the different periods of storage of red latossol soil was compared with the number of colonies obtained immediately after removal of soil samples (time zero). The number of total bacteria and actinomycetes in the samples remained practically unchanged throughout the storage period. The number of Gram-negative bacteria decreased by as much as 69% compared to control, while the number of Bacillus spp and of fungi increased 1.9 to 4.9 times starting from the 12th week in samples stored at 5oC. Except for the variations observed in fungal counts, the remaining groups of bacteria practically showed the same variation in number of colonies in soil samples stored at 5oC and -12oC

ANTIBIOTIC PRODUCTION BY STREPTOMYCES HYGROSCOPICUS D1.5: CULTURAL EFFECT

In an attempt to screen out new potent antibiotic producers from soil, Streptomyces hygroscopicus D1.5 was isolated and was found antagonistic to both bacteria and fungi. It could utilise arginine as nitrogen source and glycerol as carbon source at 0.75 g/l and 11.5 g/l level, respectively for maximum antibiotic yield