Estudo do crescimento de Ceriporiopsis subvermispora em culturas submersas para a produção de inóculos destinados ao processo de biopolpação / Studies on the submerged culturing of Ceriporiopsis subvermispora for inocolum production used in biopulping processes

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

21/08/2009

RESUMO

The present work evaluated suitable systems for producing Ceriporiopsis subvermispora mycelium in submerged cultures. Mycellium produced was used in subsequent inoculation of wood chips in biopulping processes. The development of appropriated technologies for producing large amounts of inoculum may be a key step in biopulping, since currently there are no established processes designed to produce basidiomycetes mycelium to supply biopulping demands. Even a small biopulping plant (200 ton pulp / day) may require about 1 kg of dry mycelium/day, taking into account inoculation of 5 g of dry mycelium/ton of wood to be biotreated. Thus, the success of this process may depend on the low cost of large scale fungal inoculum production. The experiments were conducted initially in 250 mL Erlenmeyer flasks containing 20 mL of liquid medium. In a second step, the experiments were conducted in bioreactors of 1.5 L (Bioflo-NewBrunswick) and finally in a bioreactor of 14 L. In the latter case, the bioreactor has been designed and constructed in order to minimize the effects of shear stress during cultivation and supply suitable aeration levels. Culture broths were composed of 2.4% potato extract and 0.7% yeast extract (BD-EL) or 2.0% sucrose and 3.2% of corn steep liquor (SM) that represent a potentially lower cost culture broth. The total biomass obtained in flask-cultures with SM broth was similar to that obtained with DB-EL. Cultures performed in the subsequent bioreactor used then the SM broth. The higher level of fungal biomass obtained in the cultures performed in the 1.5 L-stirred bioreactor was 7.0 g/L after 12 days. The highest mycelium yield was observed from the 7th day of cultivation, reaching 0.93 g/L.day and 6.5 g/L total biomass. In the 14 L-bioreactor, 3 experiments were performed in different conditions (called A, B and C). In cultivation A, no interventions were performed to correct the culture pH or the level of available nutrients over 14 days of culturing. In culture B pH was controlled to keep it between 4.0 and 5.0. Cultivation C was carried out with addition of sucrose (final concentration of 5 g/L) after 5 days of growth. All cultures were monitored with basis on the biomass produced, culture pH, residual sugar content and dissolved O2 levels. In general, biomass accumulation was always followed by sugar consumption, decrease in dissolved O2 levels and a rising tendency for the pH values. The highest biomass amount was obtained in culture C (14.1 g / L), corresponding to a yield of 1.72 g/L.day. The presence of clamydospores was observed in all cultures, whereas in culture C (in 14 L bioreactor) it appeared at the lowest amounts. This fact suggested that culture C presented the lowest stress level for the fungus, including low hypha shear stress and low nutritional depletion. The viability of inoculum prepared, both mycelium and clamydospores, was checked by culturing them on Eucalyptus grandis wood chips. Both inoculum types (prepared from the 14 L-bioreactor) were efficient on colonizing wood chips and to produce the manganese peroxidase enzyme.

ASSUNTO(S)

reatores bioquímicos biochemical reactor biopolpação biopulping ceriporiopsis subvermispora ceriporiopsis subvermispora fermentação submersa submerse fermentation

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