The regulation of α-amylase production inBacillus licheniformis

Discovery, development and exploitation of steady-state biofilms

Early in vitro biofilm models go back even beyond the invention of the word 'biofilm'. In the dental field, biofilms were simply known as dental plaque and many of the first in vitro models were termed 'artificial mouth microcosm plaques'. The purpose of this review is to highlight important elements of research from over the years regarding in vitro biofilm models, including data from our own laboratories. This helps us to interpret the models and point the way to the future development of biofilm testing. Many hypotheses regarding biofilm phenomena, particularly ecology, metabolism and physiology of volatile sulphur compounds (VSCs) and volatile organic compound (VOC) production could potentially be supported or disproved. In this way, the methods we use for screening biologically active agents including inhibitors, biocides and antimicrobial compounds in general can be improved. Hopefully, any lessons learnt in the past may be of value for the future. In this review, we focus around the need for growth rate controlled long-term biofilms; being continuously monitored using recent technical advances in bioluminescence, selective real-time electrodes, pH electrodes and continuous on-line analysis of the gas phase (both qualitatively and quantitatively). These features allow for accurate determination of growth rate and/or metabolic rate as well as pave the way towards automated assays and fine control of metabolism; impossible to achieve according to conventional biofilm theory. We also attempt to address the questions; can biofilm systems be improved to maintain long term 'real' or 'true' steady states over weeks or months, or are we limited to quasi-steady state systems for a limited period of time.

Evaluation of In Vitro Anti-Inflammatory Activities and Protective Effect of Fermented Preparations of Rhizoma Atractylodis Macrocephalae on Intestinal Barrier Function against Lipopolysaccharide Insult

Lipopolysaccharide (LPS), a potent inducer of systemic inflammatory responses, is known to cause impairment of intestinal barrier function. Here, we evaluated the in vitro protective effect of an unfermented formulation of Rhizoma Atractylodis Macrocephalae (RAM), a traditional Chinese herbal medicine widely used in the treatment of many digestive and gastrointestinal disorders, and two fermented preparations of RAM, designated as FRAM-1 (prepared in Luria-Bertani broth) and FRAM-2 (prepared in glucose), on intestinal epithelial cells (IECs) against LPS insult. In general, fermented formulations, especially FRAM-2, but not unfermented RAM, exerted an appreciable protective effect on IECs against LPS-induced perturbation of membrane resistance and permeability. Both fermented formulations exhibited appreciable anti-inflammatory activities in terms of their ability to inhibit LPS-induced gene expression and induced production of a number of key inflammatory mediators and cytokines in RAW 264.7 macrophage cells. However, in most cases, FRAM-2 exhibited stronger anti-inflammatory effects than FRAM-1. Our findings also suggest that suppression of nuclear factor- κ β (NF- κ β ) activity might be one of the possible mechanisms by which the fermented RAM exerts its anti-inflammatory effects. Collectively, our results highlight the benefits of using fermented products of RAM to protect against LPS-induced inflammatory insult and impairment in intestinal barrier function.

Production and immobilization of alpha-amylase from Bacillus subtilis

Alpha-amylase production by Bacillus subtilis was studied under different cultivation conditions. The maximum alpha-amylase production occurred after an incubation period of 48 h, temperature 40 degrees C and pH 7.5. Among the defined carbohydrates, starch (1%) was the best carbon source. The organism grew better and produced high levels of alpha-amylase using peptone as nitrogen source. The produced alpha-amylase was immobilized on various carriers by different methods and the properties of the enzyme were compared before and after immobilization. The optimum pH of the immobilized enzyme was changed to acidic range. The optimum reaction temperature of immobilized enzyme was shifted slightly to 70-80 degrees C. Both of Km values and Vmax and thermal stability of immobilized enzyme were found to be higher than that of free one. Among the tested metals CaCl2 exerted a stimulating effect on the activity of alpha-amylase.

Thermostable alpha-amylase production by an extreme thermophile Bacillus thermooleovorans

AIMS

alpha-Amylase production by a newly isolated thermophile, Bacillus thermooleovorans, was studied under different cultivation conditions.

METHODS AND RESULTS

The influence of various carbon and nitrogen sources on alpha-amylase production was quantified in batch fermentation in shake flasks. Starch and tryptone were observed to be the ideal carbon and nitrogen sources, respectively. Cultivation of the organism in a chemically defined medium consisting of glucose, riboflavin, cysteine, MgSO4, K2HPO4 and NaCl led to a near twofold increase in the production of alpha-amylase in comparison with that in the complex medium. The increase in enzyme production was achieved using vitamins and amino acids. When the organism was grown in a laboratory fermenter in the optimized complex medium, the noticeable effects were the near abolition of the lag phase, a 2.2-fold increase in enzyme production and a reduction in optimal production time from 12 to 4-5 h.

CONCLUSION

Enhancement of amylase production was achieved under various cultivation conditions.

SIGNIFICANCE AND IMPACT OF THE STUDY

Bacillus thermooleovorans produces a calcium-independent and thermostable amylase which can find use in starch saccharification.

Production and partial characterization of thermostable and calcium-independent alpha-amylase of an extreme thermophile Bacillus thermooleovorans NP54

AIM

An investigation was carried out on the production of alpha-amylase by Bacillus thermooleovorans NP54, its partial purification and characterization.

METHODS AND RESULTS

The thermophilic bacterium was grown in shake flasks and a laboratory fermenter containing 2% soluble starch, 0.3% tryptone, 0.3% yeast extract and 0.1% K2HPO4 at 70 degrees C and pH 7.0, agitated at 200 rev min(-1) with 6-h-old inoculum (2% v/v) for 12 h. When the enzyme was partially purified using acetone (80%[v/v] saturation), a 43.7% recovery of enzyme with 6.2-fold purification was recorded. The KM and Vmax (soluble starch) values were 0.83 mg ml(-1) and 250 micromol mg(-1) protein min(-1), respectively. The enzyme was optimally active at 100 degrees C and pH 8.0 with a half-life of 3 h at 100 degrees C. Both alpha-amylase activity and production were Ca2+ independent.

CONCLUSIONS

Bacillus thermooleovorans NP54 produced calcium-independent and thermostable alpha-amylase.

SIGNIFICANCE AND IMPACT OF THE STUDY

The calcium-independent and thermostable alpha-amylase of B. thermooleovorans NP54 will be extremely useful in starch saccharification since the alpha-amylases used in the starch industry are calcium dependent. The use of this enzyme in starch hydrolysis eliminates the use of calcium in starch liquefaction and subsequent removal by ion exchange.

The production of alpha-amylase in batch and chemostat culture by Bacillus stearothermophilus

The production of alpha-amylase (alpha-1,4-glucan 4-glucanohydrolase; EC 3.2.1.1) by a strain of Bacillus stearothermophilus isolated from leaf litter was investigated in a tryptone-maltose medium at 55 degrees C in batch and chemostat culture. Amylase production was growth-limited and restricted to the exponential phase in batch culture. The enzyme yield was reduced by 40% when the culture pH was maintained at pH 7.2. Amylase production in chemostat culture was influenced by the growth rate throughout the dilution rate range used.