Acetobacter pasteurianus DSM 3509 produces cobalamin

Abstract

Seed coat is an important tissue for the regulation of imbibition and maintenance of the integrity of seed, and it is also the first seed barrier encountered by pests and pathogens. Seed cotyledons contain an array of proteins that may be involved in the protection of quiescent seeds against fungi. Now we know that seed coat from Theobroma cacao L. seeds contains an antifungal activity. In the present study inhibition tests of seed coat extracts against microorganisms isolated from cocoa bean fermentations were performed. Seed coat was extracted using surfacesterilization and filter-sterilization. To determine antifungal activity in seed coat extract agar diffusion and broth microdilution tests were used. Seed coat extract can inhibit growth of fungi (e.g. Aspergillus niger, Aspergillus flavus, Aspergillus parasiticus, Mortierella isabellina, Penicillium citrinum, Penicillium purpurogenum, Penicillium roquefortii). and yeasts (e.g. Candida krusei, Candida lipolytica, Candida guilliermondii, Cryptococcus laurentii, Rhodotorula mucilaginosa, Rhodotorula rubra, Saccharomyces cerevisiae, Schizosaccharomyces pombe). No inhibition effect could be detected against gram positive bacteria (e.g. Bacillus subtilis, Staphylococcus aureus, Lactobacillus plantarum, Lactobacillus acidophilus, Lactobacillus casei, Lactobacillus fermentum, Lactobacillus reuteri, Propionibacterium freudenreichii) and gram negative bacteria (e.g. Escherichia coli, Acetobacter pasteurianus, Acetobacter tropicalis, Acetobacter pomorum, Gluconobacter frateurii, Acetobacter orientalis). The minimum inhibitory concentration (MIC) of seed coat extract was determined. 25 mg/mL of seed coat extract can inhibit growth of fungi (e.g. Penicillium citrinum, Aspergillus niger, Penicillium purpurogenum), and 10 mg/mL seed coad extract can inhibit growth of yeasts (e.g. Saccharomyces cerevisiae, Rhodotorula rubra, Candida lipolytica). Nisin production in tofu by fermentation Nicole Illas, Raphael Cziskus, Caterina Hunniger, Agata Segieda, Xuan Zhu, Markus Fischer, Bernward Bisping University of Hamburg, Institute of Food Chemistry, Division of Food Microbiology and Biotechnology, Biocenter Klein Flottbek, Ohnhorststr. 18, D-22609 Hamburg, Germany Division of Food Chemistry, Bundesstr. 45, D-20146 Hamburg, Germany Tofu has a high nutritional content but on the other hand it can easily be spoiled. In Indonesia tofu production takes place mostly in small factories without an opportunity for pasteurization. Nisin production in tofu by fermentation with Lactococcus lactis ssp. lactis DSM 20729 may be a possibility to preserve tofu. The fermentation of tofu cubes (2*2 cm) submerged in water was performed for two days. Two methods of detection of nisin in fermented tofu were tested and compared by using inhibition test (modified method of Pongtharangkul and Demirci 2004), and a liquid chromatography electrospray ionization tandem mass spectrometry method (LC-ESI-MS/MS), based on ISO/TS 27106:2009. The detection limit was significantly lower by using the inhibition test. The nisin content was 0.19 mg/kg in tofu and 0.06 mg/L in liquid substrate. In comparison to this the detection limit for nisin using LC-ESI-MS/MS was 0.34 mg/kg in tofu. Matrix calibration of the liquid substrate could not be carried out by LC-ESI-MS/MS, because the background noise of the matrix was too high. Furthermore the production and distribution of nisin in tofu cubes was investigated. The nisin concentration on the surface of tofu was 2.64 mg/kg and so it was nine times higher compared to the interior of tofu. The optimum storage condition for fermented tofu was a combination of low temperature and low pH-value. An alternative to preserve tofu may be fermentation of tofu with L. latis ssp. lactis. Nisin concentration of complete tofu cubes could be successfully determined by using both methods. The inhibition test proved to be more sensitive for nisin detection in tofu. Pongtharangkul T, Demirci A (2004) Evaluation of agar diffusion bioassay for nisin quantification. Appl Microbiol Biotechnol 65: 268-272 International Organization for Standardization: ISO/TS 27106 (2009) Cheesedetermination of nisin A content by LC-MS and LC-MS/MS. Geneva, Switzerland