Simultaneous Biodegradation of Phenol and n-Hexadecane by Cryogel Immobilized Biosurfactant Producing Strain Rhodococcus wratislawiensis BN38

The capability of the biosurfactant-producing strain Rhodococcus wratislawiensis BN38 to mineralize both aromatic and aliphatic xenobiotics was proved. During semicontinuous cultivation 11 g/l phenol was completely degraded within 22 cycles by Rhodococcus free cells. Immobilization in a cryogel matrix was performed for the first time to enhance the biodegradation at multiple use. A stable simultaneous hydrocarbon biodegradation was achieved until the total depletion of 20 g/l phenol and 20 g/l n-hexadecane (40 cycles). The alkanotrophic strain R. wratislawiensis BN38 preferably degraded hexadecane rather than phenol. SEM revealed well preserved cells entrapped in the heterogeneous super-macroporous structure of the cryogel which allowed unhindered mass transfer of xenobiotics. The immobilized strain can be used in real conditions for the treatment of contaminated industrial waste water.

Effect of the Carbon Concentration, Blend Concentration, and Renewal Rate in the Growth Kinetic ofChlorellasp.

The microalgae cultivation can be used as alternative sources of food, in agriculture, residual water treatment, and biofuels production. Semicontinuous cultivation is little studied but is more cost-effective than the discontinuous (batch) cultivation. In the semicontinuous cultivation, the microalga is maintained in better concentration of nutrients and the photoinhibition by excessive cell is reduced. Thus, biomass productivity and biocompounds of interest, such as lipid productivity, may be higher than in batch cultivation. The objective of this study was to examine the influence of blend concentration, medium renewal rate, and concentration of sodium bicarbonate on the growth ofChlorellasp. during semicontinuous cultivation. The cultivation was carried out in Raceway type bioreactors of 6 L, for 40 d at 30°C, 41.6 µmol m−2 s−1, and a 12 h light/dark photoperiod. Maximum specific growth rate (0.149 d−1) and generating biomass (2.89 g L−1) were obtained when the blend concentration was 0.80 g L−1, the medium renewal rate was 40%, and NaHCO3was 1.60 g L−1. The average productivity (0.091 g L−1 d−1) was achieved with 0.8 g L−1of blend concentration and NaHCO3concentration of 1.6 g L−1, independent of the medium renewal rate.

Immobilization of Polymethylgalacturonase Producing Aspergillus niger on Luffa Sponge Material

The vegetable sponge of Luffa cylindrica was studied as a matrix for the immobilization of Aspergillus niger 26. p roducer of polymethylgalacturonase (PMG). Entrapped spores could grow and multiply within the lattice of the sponge. The influence of loofa sponge inoculum content, initial spore inoculum content, and du ration of the growth cycle on the enzyme activity and mycelium growth was studied. The best yield of PMG was reach ed with 1 piece of loofa sponge (approx. 0.10 g dry weight), 109 spores per g carrier and 48 h duration of one cycle. Data obtained during long-term semicontinuous cultivation showed that production capacity increased significantly and the production period was extended more than 10 times compared with the free cell culture.