引起酸奶制品发生后酸化的主要发酵剂菌及性质

将培养物中保加利亚乳杆菌与嗜热链球菌调节为相同 pH值 (4 50 )、起始相同菌数7 4× 1 0 7个 /ml后分别贮存 (2 5℃ ) ,在贮存第 1 1天嗜热链球菌的 pH值为 4 57,保加利亚乳杆菌的为 3 85。将保加利亚乳杆菌确定为导致后酸化发生的主要发酵剂菌 ,是其细胞壁或细胞膜的性质保护了乳糖酶活性。

Effects of Material Physical Properties on White-rot Fungi Mycelial Growth

[ Objective] The research aimed to study effects of material physical properties on white-rot fungi mycelial growth and provide theoretical basis for further expanding the application range of white-rot fungi. [ Method Four common species of white-rot fungi were cultivated by wood meal fowl dung mixture in test tube and culture dishes. The relationship between physical properties of culture material and the growth of these mycelials were studied. [Result] The results showed the water retention capacity of culture material was decreased with the increasing of its grain size and porosity, but the decrease of its specific gravity reduced the material water retention. And the dehydration rate of medium prepared with these materials at the same moisture conditions tended to increase. These physical properties of material, such as grain size, specific gravity, porosity, water retention and water drainage, influenced the growth of white-rot fungi mycelial by affecting the moisture and ventilation condition of media. The results hinted that above material physical properties had feedback effects on the growth of white-rot fungi mycelia. [ Conclution] Physical properties of culture material have significant effects on the growth of white-rot fungi mycelial.

Effects of Applying Bio-bacterial Fertilizer on Aroma Components of Flue-cured Tobacco

Objective] This research aimed to investigate the effects of bio-bacterial fertilizer on quality of flue-curved tobacco. [Method] The various concentrations of bio-bacterial fertilizer were applied to flue-cured tobacco as leaf fertilizer and base fertilizer respectively. [Result] The effect of bio-bacterial fertilizer on flue-cured tobac-co differed among different treatments. Compared with the control, the bio-bacterial fertilizer significantly affected the quality of flue-cured tobacco. Among al the treat-ments, Treatment 3（leaf fertilizer） showed the best treatment effect, and it significant-ly improved the quality of flue-cured tobacco. [Conclusion] The bio-bacterial fertilizer showed significant improving effect on quality of flue-cured tobacco if spayed as leaf fertilizer.

Purification and Characterization of a Versatile Peroxidase from Edible Mushroom Pleurotus eryngii

A versatile peroxidase (VP-Peco60-7 ) was generated and purified from the liquid culture of Pleurotus eryngii. The purification procedure included ammonium sulfate precipitation, ion exchange chromatography, and gel chromatography. The molecular weight and isoelectric point (pI) of VP-Peco60-7 were determined to be approxi-mately 40 kDa and 4.1, respectively. By N-terminal sequence determination and peptide mapping analysis, VP-Peco60-7 was found to be similar to the versatile peroxidase isoenzyme VPL1, which was previously isolated from liquid cultures of the same species. However, the molecular weight and pI of VP-Peco60-7 were different from those of versatile peroxidases of liquid cultures, implying that the VP-Peco60-7 in this study is of a novel type. With 2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) as a substrate, the maximal enzyme activity was obtained at 50 °C and pH 3.0. The catalysis of ABTS by VP-Peco60-7 was expressed by the Michaelis-Menten equa-tion. At 50 °C and pH 3.0, the maximum velocity (V max ) was 188.68 U·mg-1 and the michaelis constant (K m ) was 203.09 μmol·L-1 .

In vitro Antimicrobial Activity and Phytochemical Screening of Local Plants

Antimicrobial activity of extracts of local plants was evaluated, with two strain i.e E. coil and S. aurri （gram positive and gram negative） microorganisms. The in vitro anti bacterial activity was performed by agar disc diffusion method. The most active antibacterial plants were S. trifiliatus and A. mexicana. The significant antibacterial activity of active extracts was compared with the standered, antimicrobics, streptomycin （10 μg/disc）. The results obtained in the present study suggest that S. trifoliatus and A. mexicana can be used in treating diseases caused by the test organism.

Collective motion of bacteria and their dynamic assembly behavior

In recent years, active matter systems have attracted considerable attentions due to their complex dynamic behaviors in physical and material science. In particular, microorganism systems have served as model systems for observing dynamic assembly and collective motility of active particles and significant progresses have been made on in-depth understanding of how high density bacteria colony behaves in the non-equilibrium state. In this mini-review, we mainly focus on the collective motion of bacteria and their dynamic assembly from four aspects： （1） the general phenomenon and biological mechanism of bacterial collective motion; （2） the common experimental techniques for studying bacterial motility; （3） some active systems on exploring bacterial collective behavior, which include both non-restricted free suspensions and those in relative confined geometric space; （4） the phenomenological and descriptive statistical methods and physical models on the underlying laws that lead to large-scale coordinate patterns in multicellular systems. This review aims to give a general picture of the collective motion in bacterial active matter systems experimentally and theoretically in order to reflect the interplays between individuals among populations in motion. It is expected that the general regulation rules related to the boundary effects in the complex systems and materials can be elucidated to some extent.