Effective Immobilization of Agrobacterium sp. IFO 13140 Cells in Loofa Sponge for Curdlan Biosynthesis.

Curdlan production by Agrobacterium sp. IFO13140 immobilized on loofa sponge, alginate and loofa sponge with alginate was investigated. There was no statistically-significant difference in curdlan production when the microorganism was immobilized in different matrices. The loofa sponge was chosen because of its practical application and economy and because it provides a high stability through its continued use. The best conditions for immobilization on loofa sponge were 50 mg of cell, 200 rpm and 72 h of incubation, which provided a curdlan production 1.50-times higher than that obtained by free cells. The higher volumetric productivity was achieved by immobilized cells (0.09 g/L/h) at 150 rpm. The operating stability was evaluated, and until the fourth cycle, immobilized cells retained 87.40% of the production of the first cycle. The immobilized cells remained active after 300 days of storage at 4 °C. The results of this study demonstrate success in immobilizing cells for curdlan biosynthesis, making the process potentially suitable for industrial scale-up. Additional studies may show a possible contribution to the reduction of operating costs.

Ultrafiltration system for cyclodextrin production in repetitive batches by CGTase from Bacillus firmus strain 37.

This study aimed to improve the yield of cyclodextrins (CDs) production in repetitive batches. An innovative ultrafiltration system was used to remove the inhibitory products that accumulated in the medium and to recover the enzyme. The assays were performed with the CGTase from Bacillus firmus strain 37 in purified, semi-purified, and crude extract forms. Maltodextrin (10% w/v) and corn starch (5% w/v) were used as substrates. After eight repetitive 24-h batches, the yield of ß-CD obtained with the purified enzyme and the corn starch substrate was 0.54 mmol/L/h, which was 36% greater than that observed with the 10% maltodextrin substrate. The crude CGTase extract with the corn starch substrate showed a productivity of 0.38 mmol/L/h, which was 29% lower than using the purified enzyme and the corn starch substrate but 7% higher than using the purified enzyme and the maltodextrin substrate. The crude extract, assayed with the corn starch substrate in the presence of 10% ethanol reached 0.43 mmol/L/h productivity, which was 12% higher compared to the assay without ethanol. The semi-purified enzyme was assayed with the corn starch substrate in the presence of 10% ethanol for eight batches lasting 12 h and an excellent selectivity for the ß-CD was obtained, reaching a mean percentage of 96.0%. Therefore, this ultrafiltration system enabled several batches of CD production, with efficient removal of products inhibitory to the CGTase and recovery of the enzyme. The possibility of industrial application of this system is promising.

Cyclodextrin glycosyltransferase production by free cells of Bacillus circulans DF 9R in batch fermentation and by immobilized cells in a semi-continuous process.

Cyclodextrin glycosyltransferase (CGTase) catalyzes starch conversion into cyclic or linear oligosaccharides, important industrial products for the complexation of non-polar substances. In this work, conditions to increase CGTase production from Bacillus circulans strain DF 9R were optimized by two systems. On one hand, free cells were grown in batch fermentation experiments to optimize aeration and pH. The highest activity (1.47 ± 0.21 U ml(-1)) was achieved after 48 h of growth, aeration of 1.5 vvm and pH regulated to 7.6. On the other hand, bacterial cells were immobilized on loofa and synthetic sponge, and used for CGTase production in a semi-continuous process. An initial biomass of 30 mg of lyophilized cells and an immobilization time of 24 h with loofa or synthetic sponge were enough to achieve increased production of CGTase: 0.91 ± 0.10 and 0.95 ± 0.11 U ml(-1), respectively. Sponges with immobilized bacteria were reused in 12 successive cycles. Besides, in our conditions, CGTase was not adsorbed onto the supports used for immobilization, which ensured the total recovery of the enzyme from the culture medium. The two CGTase production processes studied showed similar productivity and could be potentially scaled up.

Selection of microorganisms degrading S-Metolachlor herbicide

The aim of this work was to study herbicide degradation through selected microorganisms from humus and soil subjected to different plantation systems. The following bacterial species were identified: Klebsiella pneumoniae pneumoniae GC s.B strain 1, Pseudomonas alcaligenes, Enterobacter aerogenes GC s.A and Klebsiella pneumoniae pneumoniae GC s.B strain 2. Growth studies yet suggested the possibility of a very long lag phase. Although, culture with the herbicide presented biofilm formation and there were color changes in the herbicide that could have interfered with the espectrophotometry readings. After 5 days of incubation at 35°C, the difference in the concentration of herbicide was 14.42 percent on average and after 10 days, 35.01 percent.

Os herbicidas representam 65 por cento do consumo geral, sendo que o S-Metolachlor é um dos mais utilizados e está trazendo preocupações ambientais. Objetivamos detectar a degradação do S-Metolachlor por microorganismos de solos sob plantio. Foram identificadas as espécies bacterianas: Klebsiella pneumoniae pneumoniae GC s.B linhagem 1, Pseudomonas alcaligenes, Enterobacter aerogenes GC s.A e Klebsiella pneumoniae pneumoniae GC s.B linhagem 2. Resultados da curva de crescimento por espectrofotometria não permitiram definir diferentes fases, levando a pensar em uma fase Lag longa. Frascos de cultura demonstraram a formação de biofilme, provocando mudança na cor do herbicida, interferindo na leitura do crescimento. É possível a existência de fase Log, mas não detectável pelo método. Após 5 dias de incubação a 35°C, a diferença média de concentração do S-Metolachlor foi de 14.42 por cento, e em 10 dias, 35.01 por cento. Observou-se o aparecimento de um halo em volta das colônias, o que corrobora a hipótese de degradação microbiana do herbicida.