A bacterial strain capable of producing a novel bioflocculant was isolated from a biofilm sample and identified as Bacillus megaterium G31. The highest biopolymer yield was achieved when the organism was cultivated in a medium containing acetate as the so

식품 및 발효공업의 균체 제거에 이용할 수 있는 새로운 미생물 응집체를 개발할 목적으로 토양에서 분리한 Bacillus megaterium 의 응집제 생산 특성을 조사한 결과 sucrose 2.0%, NaNO_3 0.3%, tryptone 0.01%, beef extract 0.01%, MgSO_4 0.05%, CaCO_3 0.005%가 최적 배양배지로 조사되었으며 최적배지에서의 응집활성은 257.8 unit로 기초배지에 비해 응집활성이 약 161% 증가하였다. 한편 본 균주는 탄소원 및 무기염의 첨가에 의해 응집활성이 크게 영향을 받았으나 질소원의 경우 다른 성분에 비해 영향이 크지 않은 것으로 조사되어 본 균주가 생산한 응집체는 균체외 다당류의 일종인 것으로 추측된다. 또한 조정제 응집제에 대한 정색반응 결과 생산 응집제를 조정제한 후 정색반응 실험 결과는 비환원성 당으로 fructose를 함유하지 않은 다당의 일종인 것으로 추측되었다.

미생물 응집제 생산균주를 토양에서 분리하고 응집활성이 가장 높은 CH-23 균주를 분리하여 Bacillus megaterium CH-23으로 동정하였다. 분리균의 응집제 생산조건을 조사한 결과 수크로오스 2%, NaNO_3 3%, K_2HPO_4 0.1%, NaCl 0.5%, MgSO_4·7H_2O 0.5%, tryptone 0.01%의 구성된 배지를 pH 7.0으로 조절하고 25∼30℃에서 120rpm으로 배양하였을 때 정상기에서 응집활성이 가장 높았다. 배지에 Mn^2+(0.01% MnSO_4)을 가하면 약 57%의 응집활성이 증가되었고 Mg^2+(0.01% MgSO_4·7H_2O)와 Ca^2+(0.01% CaCO_3)도 응집활성을 48%와 33%씩 증가시켰다.

Various antimicrobial drug screen tests have been used in order to ensure food safety. However, the conventional screen teats, the Swab Test on Premises(STOP, USA), the Calf Antibiotic and Sulfa Teat(CAST, USA) and the European Economic Community 4-plate Test(FPT, EU) are not sufficiently rapid or sensitive enough to detect low levels of sulfa drugs in meat. We developed a new screen test kit for the determination of the antimicrobial residues in meat called the Bacillus megaterium Disk AssayBmDA). A comparison of BmDA with the older screen tests showed BmDA was as good as the older ones with several advantages. The new test kit is faster-it can be read in 4-6 hours instead of 16-18 hours. Moreover, BmDA can discriminate sulfa drugs from other antimicrobial drugs because p-aminobenzoic acid countacts the inhibiting action of sulfa drugs. Minimum detectable levels of sulfa drugs were significantly improved at the level of 0.025-0.1 ppm compared with the level of 1.0 ppm in FPT. A comparison of BmDA with the older screen tests in HPLC confirmed meat samples exeeded the Korean tolerance value of 0.1 ppm showed BmDA was the most sensitive in the microbiological screen tests. As the microbiological screen tests have already known, a person familiar with simple laboratory techniques should have no difficulty in using it to detect antimicrobial residues in meat. This would be a simple, economic method of antimicrobial residues detection which might be succesfully used by many laboratories.

This study was performed to investigate the nutritional conditions controlling keratinase activity in Bacillus megaterium F7-1. B. megaterium F7-1 produced keratinase using chicken feather as a sole source of carbon, nitrogen and sulfur. Addition of the feather medium with glucose enhanced keratinase production (68.9 U/ml), compared to control without glucose (63.2 U/ml). The synthesis of keratinase was repressed by addition of NH4Cl in B. megaterium F7-1. The highest keratinase production (70.9 U/ml) was obtained with the feather medium containing glucose and MgSO4·7H2O. Keratinase was produced in the absence of feather (4.9 U/ml), indicating its constitutive synthesis. Feather degradation resulted in free SH group formation. B. megaterium F7-1 effectively degraded chicken feather meal (86%), whereas duck feather, human nail, human hair and sheep wool displayed relatively low degradation rates (8-34%).