Aims:  To characterize and optimize a novel Bacillus pumilus strain isolated from biological waste which produces protease with excellent dehairing effect. This newly isolated strain could be utilized in the industrial leather dehairing process. Methods and Results:  Bacterial strains secreting proteases were screened from biological wastes. Positive clones were further characterized by analysing their efficacy in dehairing and effects on collagen integrity. Among 171 colonies tested, a strain BA06, identified as B. pumilus, was picked owing to its efficient dehairing capabilities with minimal impact on collagen. By combined mutagenesis using UV, N‐methyl‐N′‐nitro‐N‐nitrosdguanidine and Co60−γ‐rays, this strain was further improved with regard to its alkaline protease production. The alkaline protease activity of the mutant strain SCU11was greatly improved up to 6000 U ml−1, in comparison with its parent strain BA06 of 1200 U ml−1. Conclusions:  By using screening and mutagenesis methods, we have successfully created a B. pumilus strain that can produce high levels of alkaline proteases that are able to efficiently remove hair from skin with minimal damage on the collagen. Significance and Impact of the Study:  This strain could be used in commercial alkaline protease production for leather dehairing.

This paper examines the interaction between the spatial variations in binder concentration (i.e. cement slurry concentration) and in situ water content, in cement-mixed soil, using field and model data as well as statistical analysis and random field simulation. The field data are first analysed to shed light on the spatial variation in the in situ water content, including its scale of fluctuation. A statistical model is then developed which takes into account the variation in binder concentration and in situ water content. This leads to a two-parameter model for the prediction of the mean, variance and probability distribution function of the strength of the cement-treated soil. The scale of fluctuation for the variation in binder concentration arising from imperfect mixing within a cement-mixed column is then examined using centrifuge model data. This indicates that the scale of fluctuation in binder concentration is much shorter in range than that of the in situ water content. The combined effect of these two scales of fluctuation is then studied by simulating the resulting random field using Monte-Carlo simulations. This indicates that the size of the sampling region has a significant effect on the scale of fluctuation that is captured. If the sampling region is of a similar size to the column diameter, the measured scale of fluctuation reflects that of the binder concentration. As the size of the sampling region increases, so does the measured scale of fluctuation. This explains the wide range of scales of fluctuation that have been reported for cementtreated soil. To capture both scales of fluctuation in core sampling, some boreholes should be sunk at close spacings of less than a column diameter, in order to capture short-range variation.

This study examines the effect of geometric imperfections arising from variations in both the diameter and orientation of jet-grouted columns on the water-tightness of a jet-grouted cut-off wall. A three-dimensional discretised algorithm is used to detect and measure the discontinuities in the wall. A statistical evaluation of the gross flow rate through the cut-off wall with random flow-through pathways is carried out using Monte Carlo simulations. Based on the statistical results, a dimensionless design chart is proposed which can help engineers to devise safe and economical wall designs through trade-offs among various parameters such as target diameter, column spacing and number of rows.

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