Suelen Pereira Ruiz

Evaluation of the antibacterial activity of Piperaceae extracts and nisin on Alicyclobacillus acidoterrestris.

Alicyclobacillus acidoterrestris is a gram-positive aerobic bacterium. This bacterium resists pasteurization temperatures and low pH and is usually involved in the spoilage of juices and acidic drinks. The objective of this study was to evaluate the antibacterial activities of nisin and the species Piper (Piperaceae) on A. acidoterrestris. The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) were determined by the broth microdilution method. The species Piper aduncum had the lowest MIC and an MBC of 15.6 μg/mL and was selected for fractionation. Six fractions were obtained, and the dichloromethane fraction (F.3) had the lowest MIC/MBC (7.81 μg/mL). The dichloromethane fraction was again fractionized, and a spectral analysis revealed that the compound was prenylated chromene (F.3.7). The checkerboard method demonstrated that the crude extract (CE) of P. aduncum plus nisin had a synergistic interaction (fractional inhibitory concentration [FIC] = 0.24). The bactericidal activity of (F.3.7) was confirmed by the time-kill curve. P. aduncum, nisin, and prenylated chromene exhibited strong antibacterial activity against the spores and vegetative cells of A. acidoterrestris. The results of this study suggest that extracts of the genus Piper may provide an alternative to the use of thermal processing for controlling A. spoilage.

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.

Resistance of Alicyclobacillus acidoterrestris spores and biofilm to industrial sanitizers.

This study evaluated the adhesion and biofilm formation of Alicyclobacillus acidoterrestris on industrial orange juice processing equipment and the bactericidal efficacy of peracetic acid, sodium hypochlorite, and quaternary ammonia after biofilm formation. The efficacy of these sanitizers against the spores of this microorganism was also evaluated. Stainless steel and nylon surfaces exhibited higher cell adhesion levels than did polyvinyl chloride surfaces. Peracetic acid was the most effective in removing biofilms from all surfaces (P < 0.05) and also reduced bacterial counts by 3 log CFU/cm² on the surface of polyvinyl chloride, but the other sanitizers also reduced the bacterial counts by 2 log CFU/cm². Quaternary ammonia exhibited the optimal minimum sporicidal concentration, preventing spore germination after only 15 s of contact at a concentration of 82 ppm. The flow cytometry results indicated that the spores and cells had low incidences of plasma membrane lysis after treatment with sanitizer, suggesting that lysis is not the principal mode of action for these sanitizers on A. acidoterrestris.

Characterization of curdlan produced by Agrobacterium sp. IFO 13140 cells immobilized in a loofa sponge matrix, and application of this biopolymer in the development of functional yogurt

BACKGROUND Agrobacterium sp. IFO 13140 cells were immobilized on a loofa sponge and used to produce curdlan over five successive cycles. The interaction between microbial cells and the loofa sponge as well as the produced curdlan were characterized by Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectrometry. The purity of the curdlan was also evaluated. The storage stability of the immobilized cells was assessed and the produced curdlan was used in a functional yogurt formulation. RESULTS The average curdlan production by immobilized cells was 17.84 g L(-1) . The presence of the microorganism in the sponge was confirmed and did not cause alterations in the matrix, and the chemical structure of the curdlan was the same as that of commercial curdlan. The purity of both was similar. The immobilized cells remained active after 300 days of storage at -18 °C. The use of the produced curdlan in a functional yogurt resulted in a product with lower syneresis. CONCLUSION A large number of cells physically adhered to the surface of loofa sponge fibers, and its use as an immobilization matrix to produce curdlan was effective. The use of the produced curdlan in yogurt allowed the development of a more stable product.

BIOSYNTHESIS OF INDUSTRIAL ENZYMES BY FREE AND IMMOBILIZED Alicyclobacillus spp IN DIFFERENT MATRICES AND THE USE OF ULTRAFILTRATION IN THE ENZYMES CONCENTRATION

The biosynthesis of amylase and collagenase, produced by A. acidocaldarius and A. sendaiensis respectively, were studied, and different matrices evaluated for the microorganisms immobilization and enzymes production optimization, such as loofa sponge, alginate-sponge and alginate, followed by concentration through ultrafiltration. Using a wheat bran substrate, the amylase enzyme displayed enzymatic activity of 0.45 U mL and optimum temperature and pH conditions of 75 °C and pH 3.0, respectively. Thermal stability was in the range of 55 to 60 °C. The apparent Km and Vmax were 3.2 mg mL and 0.5 U mL, respectively. The production of collagenase by A. sendaiensis was carried out with potato dextrose broth substrate and the activity obtained was 7.2 U mL. For amylase, the best results were obtained from immobilization in loofa sponge and the use of ultrafiltration (0.67 U mL) and for the collagenase extract, from the free biomass and ultrafiltration (13.6 U mL). The use of an ultrafiltration system enabled an average increase of 54% in the activity of both enzymes. Therefore, Alicyclobacillus are capable of producing enzymes of industrial interest, with the possibility of economically viable application of the substrate, and the use of immobilization and ultrafiltration produced positive results.

Evaluation of different culture media and enrichment in orange juice upon the growth of Alicyclobacillusspp.

Bacteria of the genus Alicyiclobacillus spp. form spores and develop in acid media, leading to the spoilage of citrus juices. Brazil is the largest exporter of orange juice concentrate, and yet, it has been extensively studied due to changes in taste and smell. Several investigations have reported different culture media used to detect and enumerate Alicyiclobacillus spp. The objective of the present study was to evaluate the recovery of Alicyiclobacillus spp. spores grown in ALI, BAT, K agar and YSG media using the methodology suggested by ABECitrus. Five inocula were used, two from reference strains and three from pasteurized concentrated orange juice. Cell recovery after the enrichment in reconstituted orange juice was also analyzed. An initial population of 6 log CFU/mL was inoculated. ALI, BAT and YSG media were able to recover the initial population of all different inocula, with no significant differences between the results. When compared to BAT, however, the preparation of ALI and YSG media was simpler and had more advantages. The recovery with K agar medium was lower than the other media for all the tested inocula, with significant differences found for Alicyclobacillus acidocaldarius 0298T (3.66 log CFU/mL) and Alicyclobacillus pomorum-like CBMAI 0278 (4.11 log CFU/mL).