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The grain-producing regions of northern New South Wales and southern and central Queensland are characterised by cropping systems that are strongly dependent on stored soil moisture rather than in-crop rainfall, and tillage systems that are increasingly reliant on zero or minimum tillage. Crops are grown relatively infrequently and crop rotations are dominated by winter and summer grains (wheat [Triticum aestivum L.] and sorghum [Sorghum bicolor L. Moench], respectively), with smaller areas of grain legumes and cotton (Gossypium hirsutum L.). The grey, black, and brown Vertosols represent the more productive soils in the region under rainfed cropping, and are the focus of work reported in this study. Soil samples were collected from surface soils (0-0.30 m) across the region, utilising sites of long term tillage and residue management studies, fertiliser trials, and commercial fields to enable an assessment of the impact of various management practices on soil biological properties. A number of biological and biochemical parameters were measured (microbial biomass C, total organic C and labile C fractions, total C and N, microbial activity using FDA, cellulase activity, free living nematodes, total DNA and fatty acid profiles), and the response of wheat, sorghum, and chickpea (Cicer arietinum L.) to steam pasteurisation was assessed in glasshouse bioassays. The objective was to obtain an indication of the biological status of grain-growing soils and assess the impact of biological constraints in soils from different regions and management systems. Results showed that biological activity in cropped soils was consistently low relative to other land uses in northern Australia, with management practices like stubble retention and adoption of zero tillage producing relatively small benefits. In the case of zero tillage, many of these benefits were confined to the top 0.05 m of the soil profile. Fallowing to recharge soil moisture reserves significantly reduced all soil biological parameters, while pasture leys produced consistent positive benefits. Breaking a long fallow with a short duration grain or brown manure crop significantly moderated the negative effects of a long bare fallow on soil biology. Use of inorganic N and P fertilisers produced minimal effects on soil biota, with the exception of one component of the free-living nematode community (the Dorylaimida). The glasshouse bioassays provided consistent evidence that soil biota were constraining growth of both grain crops (sorghum and wheat) but not the grain legume (chickpea). The biota associated with this constraint have not yet been identified, but effects were consistent across the region and were not associated with the presence of any known pathogen or correlated with any of the measured soil biological or biochemical properties. Further work to confirm the existence and significance of these constraints under field conditions is needed. None of the measured biological or biochemical parameters consistently changed in response to management practices, while conflicting conclusions could sometimes be drawn from different measurements on the same soil sample. This highlights the need for further work on diagnostic tools to quantify soil biological communities, and suggests there is no clear link between measured changes in soil biological communities and economically or ecologically important soil attributes. Additional keywords: plant growth, wheat, sorghum, chickpea, bioassays., Introduction The broadacre grain cropping areas of north-eastern Australia (northern New South Wales, southern and central Queensland) occupy an area of approximately 4 Mha (Anon. 2004). Farming systems vary significantly [...]

Conditions for optimal pretreatment of eucalypt ( Eucalyptus dunnii ) and spotted gum ( Corymbia citriodora ) forestry thinning residues for bioethanol production were empirically determined using a 3 3 factorial design. Up to 161 mg/g xylose (93% theoretical) was achieved at moderate combined severity factors (CSF) of 1.0–1.6. At CSF > 2.0, xylose levels declined, owing to degradation. Moreover at high CSF, depolymerisation of cellulose was evident and corresponded to glucose (155 mg/g, ∼33% cellulose) recovery in prehydrolysate. Likewise, efficient saccharification with Cellic® CTec 2 cellulase correlated well with increasing process severity. The best condition yielded 74% of the theoretical conversion and was attained at the height of severity (CSF of 2.48). Saccharomyces cerevisiae efficiently fermented crude E. dunnii hydrolysate within 30 h, yielding 18 g/L ethanol, representing a glucose to ethanol conversion rate of 0.475 g/g (92%). Based on our findings, eucalyptus forest thinnings represent a potential feedstock option for the emerging Australian biofuel industry. [ABSTRACT FROM AUTHOR]

Abstract: Dilute sulphuric acid pretreatment followed by enzyme saccharification of Sorghum bicolor straw was undertaken to examine its potential as a feedstock in bioethanol production in Australia. Factorial design experiments evaluated the impact of pretreatment parameters on hemicellulose solubilisation and cellulose enzymatic hydrolysis. Sugar yields in prehydrolysate and saccharified liquors were found to increase with treatment severity; temperature was found to have the greatest impact. Degradation products were minimal; acetate and total phenolics peaked at 33 and 1.5mg/g respectively. Conditions for maximum hemicellulose solubilisation (2% H2SO4 for 60min at 121°C) differed to those associated with maximum glucose release from solid residue saccharifications (1% H2SO4/90min /121°C). Water extractive sugars accounted for over 20% total sugars recovered. Addition of β-glucosidase and xylanase to enzyme saccharification enhanced reaction rates and final sugar yields three-fold, whilst reducing cellulase dosage. Considering its abundance, high sugar potential and apparent ease of conversion, sorghum straw is an appropriate feedstock for the production of second generation fuels. [Copyright &y& Elsevier]

Abstract: The impacts of varying pretreatment parameters (temperature, time, and alkalinity) on enzymatic hydrolysis of sorghum straw were investigated. Following pretreatment, both solids and lignin content was found to be inversely proportional to the severity of the treatments. Higher temperatures and alkali strength were quintessential for maximising sugar recoveries from enzyme saccharifications. Total sugar release peaked when sorghum straw was pretreated in 2% NaOH at 121°C for 60min; representing a 5.6-fold higher yield compared to samples pretreated at 60°C in the absence of alkali. Similarly, 4.3-fold increases in total sugars from samples treated with 2% NaOH at 60°C for 90min, confirmed the importance of alkali inclusion. Addition of β-glucosidase and xylanase to saccharification mixtures enhanced reaction rates and final sugar yields, whilst reducing cellulase dosage 4-fold. Saccharification efficiency of pretreated solids approached 90% and 95% (w/w) with as little as 2.5 and 5.0FPU cellulase/g, respectively. [Copyright &y& Elsevier]

Abstract: A new method for extracting soil enzymes is described and a microplate method for assaying soil β-1,4-glucanases (cellulases) and β-1,3-glucanases (laminarinases). Soil samples were mechanically disrupted to produce crude enzyme extracts, and diluted preps incubated in microplates containing either carboxymethyl cellulose (CMC) to determine cellulase activity or laminarin substrate to determine laminarinase activity. The resulting glucose was measured using the fluorometric Amplex Red® glucose assay. The method was reproducible, could be completed in 1 day and measured twice as much enzyme activity than the standard passive soil enzyme extraction procedure. The method described herein facilitates the development of high-throughput soil multiplex enzymatic assays from several soil samples at one time, and is well suited to the study of functional microbial ecology. [Copyright &y& Elsevier]

d. jordan, t. vancov, a. chowdhury, l.m. andersen, k. jury, a.e. stevenson and s.g. morris. 2004.To modify a strain ofSalmonellaserotype Typhimurium to express unique marker traits and then define how the concentration of the marker in bovine faeces affects the probability of its detection by culture preceded by immunomagnetic separation (IMS).DNA encoding for the production of green fluorescent protein (gfp) and resistance to kanamycin was inserted into the bacterial chromosome ofSalm. Typhimurium. Transposon insertion was demonstrated by Southern blot hybridization. Varying amounts of one electroporant (gfpSal-1) were inoculated into suspensions of bovine faeces and attempts made to isolategfpSal-1 using a protocol based on pre-enrichment incubation, IMS and enrichment in selective media. Isolates ofgfpSal-1 were differentiated from wild strains ofSalmonellausing fluorescence under u.v. light and expression of kanamycin resistance. A logistic and Gompertz function each derived from the dose–response data partially explained the observations with the fit of the Gompertz function judged to be superior. The 10, 50 and 90% limits of detection from the Gompertz function were estimated to be 1·92, 2·03 and 2·27 CFU g−1 respectively.Reliance on the traditional concept of‘limit of detection’ could introduce unacceptable errors in the interpretation of test findings when the concentration ofSalm. Typhimurium in bovine faeces (pooled or individual) is belowca3 CFU g−1 of faeces.The dose–response curve can be used to aid the design of protocols for detectingSalmonellain individual and pooled faecal specimens. The experiments demonstrate that both reporter genes in tandem are useful for studying the performance of culture-based methods for detecting pathogens in faeces. [ABSTRACT FROM AUTHOR]