Browsing by Author "Shah, Hamid Ullah"

Now showing 1 - 2 of 2
  • Thumbnail Image
    ItemOpen Access
    Soil and transport factors in potential distribution systems for biofertilisers derived from palm oil mill residues in Malaysia
    (Elsevier, 2019-10-08) Truckell, Ian G.; Shah, Hamid Ullah; Baillie, Ian C.; Hallett, Stephen H.; Sakrabani, Ruben
    Oil palm provides an important source of edible oils and fats, accounting for >30% of total global production and >55% of the international trade in these foodstuffs. The palms produce fresh fruit bunches, comprising several hundreds of small fruitlets, which are compressed and steamed to extract the oil. Soil nutrients in oil palm estates become depleted after decades of heavy harvesting and require fertilisers. Liquid palm oil mill effluent, solid empty fruit bunches and other residues can have deleterious environmental impacts and require careful management. The problems of residue disposal and soil nutrient impoverishment can be linked and managed by composting the oil palm mill residues and distributing the biofertiliser produced back to the plantation. Using case studies from West Malaysia we present an early stage practical tool for the planning of the distribution component of such a cycle. The computer-based tool uses multiple field-based and remote sensing data sources to integrate the effects of local soil conditions, transport distances, environmental protection and management priorities and then models customised distribution plans. The tool operates at plantation level and can be augmented with detailed local data, but the approach is extensible and potentially applicable to regional or national planning.
  • Thumbnail Image
    ItemOpen Access
    Water availability affects extracellular hydrolytic enzyme production by Aspergillus flavus and Aspergillus parasiticus
    (Wageningen Academic Publishers, 2009-08-31T00:00:00Z) Alam, Sahib; Shah, Hamid Ullah; Magan, Naresh
    The objectives of this study were to examine the effect of different water activities (a(w); 0.99, 0.96 and 0.94) and time (up to 120 h) on quantitative and specific enzyme production during germination and initial growth of Aspergillus flavus and A. parasiticus strains at 25 degrees C. This is an important early indicator of potential for aflatoxin production under conducive conditions. Qualitative API ZYM generic enzyme strips were used to identify key hydrolytic enzymes produced. Subsequently, the temporal effects of a(w) on the total/specific activity of the key 4-5 hydrolytic enzymes were determined using 4-nitrophenyl substrates in a 96-well microtitre plate assay. The main enzymes produced by germinating conidia of A. flavus were esterase, lipase, acid phosphatase, beta-glucosidase and N-acetyl-beta-D-glucosaminidase, while for A. parasiticus these were alkaline phosphatase, lipase, acid phosphatase and beta- fucosidase for both total (mu mol 4-nitrophenol/min/g) and specific activity (nmol beta-nitrophenol/min/mu g protein). There were significant increases in the specific activity of all these enzymes of germinating spores of A. flavus (0-120 h) except for beta-glucosidase which was maximum at 72 h. The total/ specific activities of the enzymes produced by A. flavus were maximum at 0.99 a (w) with the exception of acid phosphatase and N-acetyl-beta-D-glucosaminidase at 0.94 a(w) For A. parasiticus, maximum total activity occurred at 0.99 aw for fucosidase activity, while specific activity was found to be higher at lower a (w) levels. These enzymes are important in early colonisation of food matrices by these species and single factors (a(w) time) and two-way interactions were all statistically significant for the enzymes assayed for both species. These enzymes could be used as an early and rapid indicator of the activity of Aspergillus section flavi species and suggests that rapid infection may occur over a wide range of a(w) conditions.