Undefined xylose media extracted from biorefinery waste for enhanced and eco-friendly production of cephalosporin C by Acremonium chrysogenum M35

Xylose-rich undefined broth, extracted from the dilute acid pretreatment wastes of barley straw, serves as resourceful media for Acremonium chrysogenum M35 culture and production of cephalosporin C (CPC). Concentrating the extract with proper reprocessing enables to prepare various concentrations of xylose broth (2%–8%). The undefined xylose media were prepared for CPC production from A. chrysogenum M35 by the addition of other nutrients. Cell growth and CPC production were the most effective at 6% xylose and additional 2% glycerol, with maximum CPC production of 9.07 g/L after 6 days, which is higher production than that in defined media prepared with laboratory-level nutrients and reagents. Investigation of autotrophic and reverse trans-sulfuration pathways for cysteine synthesis, a limited element of three precursors for CPC synthesis, supports the enhanced CPC production in undefined media. Abundance of xylose ensures a maintained NADPH concentration required for sulfate reduction and synthesis of amino sulfide such as cysteine. Cystathionine-γ-lyase activity profiling indicated more efficient biosynthesis in undefined media than in other cultures use glycerol and glucose, and the biosynthesis pathway of CPC production by the cephalosporin gene cluster (i.e. pcbC and cefG genes) was investigated. The process using undefined xylose media was designed, and process simulation program confirmed our results.     

Influence of fire severity on the regeneration,recruitment and distribution of eucalypts in the Cotter River Catchment,Australian Capital Territory

Abstract Plant responses to fire are variable between and within species and are influenced by numerous factors including fire severity. This study investigated the effects of fire severity on the regeneration and recruitment of forest eucalypts in the Cotter River Catchment, Australian Capital Territory (ACT). This study also examined the potential for the obligate seeder Eucalyptus delegatensis R.T. Baker (Myrtaceae) to expand into adjacent stands dominated by the facultative resprouter Eucalyptus fastigata H. Deane & Maiden (Myrtaceae) by seed shed and seedling establishment beyond the pre‐fire boundary. Sites were located in areas of either higher or lower fire severity, and transects were placed across the boundary of stands of E. delegatensis and E. fastigata. Species distributions, tree survival and seedling densities and heights were recorded, and the location of each boundary was determined as the region of maximum change in species composition along the transects. Eucalyptus delegatensis was the only eucalypt killed by higher severity fire. However, E. delegatensis seedling density was greater at higher severity sites than lower severity sites. Eucalyptus fastigata seedling density was low across all sites, with other eucalypts producing few, if any, seedlings. There was no evidence that E. delegatensis had increased its range into downslope stands dominated by E. fastigata. Patterns of vegetative recovery and seedling recruitment may be related to a number of factors, including differences in allocation patterns between seeders and sprouters, and the effects of overstory and understory competition. It is unclear what processes impede E. delegatensis seedling establishment beyond the stand boundary, but may involve an inability of E. delegatensis to shed seed sufficiently far downslope; unsuitable conditions for germination beyond the boundary; or, competition from a retained or resprouting overstory, despite the potential for increased dispersal distance soon after fire.     

玉米芯发酵法生物制氢

在批式培养试验中, 以牛粪堆肥为天然产氢菌源, 玉米芯为底物, 通过厌氧发酵生产氢气。系统考察了底物预处理条件、初始pH值和底物浓度对玉米芯产氢能力的影响。在初始pH 8.0, 1.0%盐酸预处理底物30 min, 底物浓度10 g/L的最佳产氢条件下, 玉米芯最大产氢能力〔每克TVS（总挥发性固体物）产氢量〕和最大产氢速率（每克TVS每小时产氢量）分别为107.9 mL /g、4.20 mL/g·h-1。玉米芯经酸预处理后半纤维素含量由42.2%下降至3.0%, 而酸预处理的玉米芯产氢前后纤维素、半纤维素和木质素含量只有少量变化。产氢菌主要用酸预处理产生的可溶性糖产氢, 故底物的酸预处理对玉米芯的发酵产氢非常重要。用傅里叶变换红外光谱(FTIR)分析显示酸预处理和产氢过程中玉米芯的特征峰发生变化, 酸预处理过程降解了底物纤维素的无定形区和半纤维素, 产氢微生物对纤维素的结晶区有破坏作用。     

Access of cellulase to cellulose and lignin for poplar solids produced by leading pretreatment technologies

Adsorption of cellulase on solids resulting from pretreatment of poplar wood by ammonia fiber expansion (AFEX), ammonia recycled percolation (ARP), controlled pH, dilute acid (DA), flowthrough (FT), lime, and sulfur dioxide (SO₂) and pure Avicel glucan was measured at 4°C, as were adsorption and desorption of cellulase and adsorption of β‐glucosidase for lignin left after enzymatic digestion of the solids from these pretreatments. From this, Langmuir adsorption parameters, cellulose accessibility to cellulase, and the effectiveness of cellulase adsorbed on poplar solids were estimated, and the effect of delignification on cellulase effectiveness was determined. Furthermore, Avicel hydrolysis inhibition by enzymatic and acid lignin of poplar solids was studied. Flowthrough pretreated solids showed the highest maximum cellulase adsorption capacity (σ_solids = 195 mg/g solid) followed by dilute acid (σ_solids = 170.0 mg/g solid) and lime pretreated solids (σ_solids = 150.8 mg/g solid), whereas controlled pH pretreated solids had the lowest (σ_solids = 56 mg/g solid). Lime pretreated solids also had the highest cellulose accessibility (σ_cellulose = 241 mg/g cellulose) followed by FT and DA. AFEX lignin had the lowest cellulase adsorption capacity (σ_lignin = 57 mg/g lignin) followed by dilute acid lignin (σ_lignin = 74 mg/g lignin). AFEX lignin also had the lowest β‐glucosidase capacity (σ_lignin = 66.6 mg/g lignin), while lignin from SO₂ (σ_lignin = 320 mg/g lignin) followed by dilute acid had the highest (301 mg/g lignin). Furthermore, SO₂ followed by dilute acid pretreated solids gave the highest cellulase effectiveness, but delignification enhanced cellulase effectiveness more for high pH than low pH pretreatments, suggesting that lignin impedes access of enzymes to xylan more than to glucan, which in turn affects glucan accessibility. In addition, lignin from enzymatic digestion of AFEX and dilute acid pretreated solids inhibited Avicel hydrolysis less than ARP and flowthrough lignin, whereas acid lignin from unpretreated poplar inhibited enzymes the most. Irreversible binding of cellulase to lignin varied with pretreatment type and desorption method. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009     

Short‐term lime pretreatment of poplar wood

Short‐term lime pretreatment uses lime and high‐pressure oxygen to significantly increase the digestibility of poplar wood. When the treated poplar wood was enzymatically hydrolyzed, glucan and xylan were converted to glucose and xylose, respectively. To calculate product yields from raw biomass, these sugars were expressed as equivalent glucan and xylan. To recommend pretreatment conditions, the single criterion was the maximum overall glucan and xylan yields using a cellulase loading of 15 FPU/g glucan in raw biomass. On this basis, the recommended conditions for short‐term lime pretreatment of poplar wood follow: (1) 2 h, 140°C, 21.7 bar absolute and (2) 2 h, 160°C, and 14.8 bar absolute. In these two cases, the reactivity was nearly identical, thus the selected condition depends on the economic trade off between pressure and temperature. Considering glucose and xylose and their oligomers produced during 72 h of enzymatic hydrolysis, the overall yields attained under these recommended conditions follow: (1) 95.5 g glucan/100 g of glucan in raw biomass and 73.1 g xylan/100 g xylan in raw biomass and (2) 94.2 g glucan/100 g glucan in raw biomass and 73.2 g xylan/100 g xylan in raw biomass. The yields improved by increasing the enzyme loading. An optimal enzyme cocktail was identified as 67% cellulase, 12% β‐glucosidase, and 24% xylanase (mass of protein basis) with cellulase activity of 15 FPU/g glucan in raw biomass and total enzyme loading of 51 mg protein/g glucan in raw biomass. Ball milling the lime‐treated poplar wood allowed for 100% conversion of glucan in 120 h with a cellulase loading of only 10 FPU/g glucan in raw biomass. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009     

Sulfite pretreatment to overcome recalcitrance of lignocellulose (SPORL) for robust enzymatic saccharification of hardwoods

This study demonstrates sulfite pretreatment to overcome recalcitrance of lignocellulose (SPORL) for robust bioconversion of hardwoods. With only about 4% sodium bisulfite charge on aspen and 30‐min pretreatment at temperature 180°C, SPORL can achieve near‐complete cellulose conversion to glucose in a wide range of pretreatment liquor of pH 2.0–4.5 in only about 10 h enzymatic hydrolysis. The enzyme loading was about 20 FPU cellulase plus 30 CBU β‐glucosidase per gram of cellulose. The production of fermentation inhibitor furfural was less than 20 mg/g of aspen wood at pH 4.5. With pH 4.5, SPORL avoided reactor corrosion problem and eliminated the need for substrate neutralization prior to enzymatic hydrolysis. Similar results were obtained from maple and eucalyptus. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009     

Community stability under different correlation structures of species’ environmental responses

The outcome of species interactions in a variable environment is expected to depend on how similarly different species react to variation in environmental conditions. We study community stability (evenness and species diversity) in competitive communities that are either closed or subjected to random migration, under different regimes of environmental forcing. Community members respond to environmental variation: (i) independently (IR), (ii) in a positively correlated way (CR), or (iii) hierarchically, according to niche differences (HR). Increasing the amplitude of environmental variation and environmental reddening both reduce species evenness in closed communities through a reduction in species richness and increased skew in species abundances, under all three environmental response scenarios, although autocorrelation only has a minor effect with HR. Open communities show important qualitative differences, according to changes in the correlation structure of species’ environmental responses. There is an intermediate minimum in evenness for HR communities with increasing environmental amplitude, explained by the interaction of changes in species richness and changes in the variance of within-species environmental responses across the community. Changes in autocorrelation also lead to qualitative differences between IR, CR and HR communities. Our results highlight the importance of considering mechanistically derived, hierarchical environmental correlations between species when addressing the influence of environmental variation on ecological communities, not only uniform environmental correlation across all species within a community.     

Mass-Spectrometry Based Characterisation of Infant Whole Saliva Peptidome

The objective of the study was to determine optimal conditions for sampling, sample processing and mass-spectrometry based analysis of infants’ salivary peptidome. Saliva was sampled in 3- and 6-month-old infants and peptide extracts were prepared. Various sample pretreatments before profiling by MALDI-ToF were evaluated and peptide identification was undertaken by MALDI-ToF/ToF or nanoLC-ESI-IT tandem MS. A fast and simple protocol (cut-off filtration at 5 kDa) was satisfactory to produce extracts where no proteolysis was detected even when no protease inhibitor was added. Optimal MALDI spectra were generated after purification on C18 tips. Variability of spectra between two samples exceeded that of the technical replicates, validating that the method is suitable to conduct differential studies. Salivary peptides, identified by means of the two complementary mass spectrometry techniques, were fragments of proline-rich proteins and histatins. The fragments originated mainly from the C-terminal protein extremities. Indications on the proteolytic systems involved and the anatomic location where they intervene are proposed.     

Improved one‐step steam pretreatment of SO2‐Impregnated softwood with time‐dependent temperature profile for ethanol production

In the production of ethanol from lignocellulosic material, pretreatment of the raw material before enzymatic hydrolysis and fermentation is essential to obtain high overall yields of sugar and ethanol. Two‐step steam pretreatment results in higher ethanol yields from softwood than the standard one‐step pretreatment process. However, the difficulty with separation and washing of the material at high pressure between the two pretreatment steps is a major drawback. In this study, a new one‐step pretreatment procedure was investigated, in which the time‐temperature profile was varied during pretreatment. The efficiency of pretreatment was assessed by performing simultaneous saccharification and fermentation on the pretreated slurries. Pretreatment of SO₂‐impregnated softwood performed by varying the temperature (190–226°C), the residence time (5–10 min), and the mode of temperature increase (linear or stepwise), resulted in recovery of about 90% of the mannose and glucose present in the raw material. The highest ethanol yield, 75% of theoretical based on the glucan and mannan content of the raw material, was obtained at pretreatment conditions of 190°C for 12 min. Similar ethanol yields were achieved when running the pretreatment as one‐step (190–200°C), two levels of temperature, at shorter residence time (7 min), which results in lower capital costs for the process. © 2010 American Institute of Chemical Engineers Biotechnol. Prog., 2010