Cloning and characterization of three compost metagenome-derived α‑L‑Arabinofuranosidases with differing thermal stabilities

>Magister Scientiae - MScSecond generation biofuels production requires a suite of lignocellulolytic enzymes, acting synergistically to liberate the fermentable monosaccharides contained within agricultural waste materials. The use of thermostable lignocellulosic enzymes in a high-temperature process represents a number of advantages over their respective mesophilic counterparts, including increased solubility of the polymeric lignocellulosic substrates, enhanced enzyme processivity and reduced risk of bacterial and/or phage contamination during fermentation (Turner et al., 2007; Viikari et al., 2007). Alpha-L-arabinofuranosidases (AFases) participate in the deconstruction of lignocellulosic materials by hydrolysing the arabinofuranosyl bonds contained within the hemicellulosic portion of lignocellulose. In this study, three AFases isolated from compost-derived metagenomic DNA were characterised. Three genes derived from the fosmid metagenomic library constructed from 70°C compost were cloned into the pET21a(+) expression vector and expressed in E. coli BL21. The heterologously expressed proteins, AFase_H4, AFase_E3 and AFase_D3, were subsequently purified and their biochemical characteristics determined. All three AFases were shown to be active between pH 4.0 and 6.0. AFase_H4 and AFase_E3 displayed the highest activity at 60oC, while AFase_D3 had an optimum temperature at 25oC. Furthermore, the three AFases had differing thermostability profiles. In particular, AFase_E3 maintains 100% residual activity following 60 min incubation at 80oC and 24 hour incubation at 60oC. All three AFases have activity upon p-Nitrophenyl-arabinofuranoside and none against a range of alternative p-Nitrophenylglycosidic substrates. Phylogenetic analysis of the catalytic domain, identified within the amino acid sequences of the AFases, suggests that these AFases belong to glycoside hydrolase (GH) family 51. The difference in the AFase primary amino acid sequence motifs were used to infer differences in thermostability. All three AFases indicated similar biochemical and biophysical characteristics. AFase_E3 was determined to be the most thermostable amongst all three AFases. In the assessment of the three AFases respective suitability for inclusion in thermogenic bioethanol production processes, AFase_E3 was concluded as a suitable candidate for hydrolysis and synergistic testing on natural substrates. AFase_D3 possess the potential to be included in novel mesophilic industrialized process

Characterisation of three novel α-L-arabinofuranosidases from a compost metagenome

Background: The importance of the accessory enzymes such as α-L-arabinofuranosidases (AFases) in synergistic interactions within cellulolytic mixtures has introduced a paradigm shift in the search for hydrolytic enzymes. The aim of this study was to characterize novel AFase genes encoding enzymes with differing temperature optima and thermostabilities for use in hydrolytic cocktails. Results Three fosmids, pFos-H4, E3 and D3 were selected from the cloned metagenome of high temperature compost, expressed in Escherichia coli and subsequently purified to homogeneity from cell lysate. All the AFases were clustered within the GH51 AFase family and shared a homo-hexameric structure. Both AFase-E3 and H4 showed optimal activity at 60 °C while AFase-D3 had unique properties as it showed optimal activity at 25 °C as well as the ability to maintain substantial activity at temperatures as high as 90 °C. However, AFase-E3 was the most thermostable amongst the three AFases showing full activity even at 70 °C. The maximum activity was observed at a pH profile between pH 4.0–6.0 for all three AFases with optimal activity for AFase H4, D3 and E3 at pH 5.0, 4.5 and 4.0, respectively. All the AFases showed KM range between 0.31 mM and 0.43 mM, Kcat range between 131 s− 1 and 219 s− 1 and the specific activity for AFase-H4, AFases-E3 and was 143, 228 and 175 U/mg, respectively. AFases-E3 and D3 displayed activities against pNP-β-L-arabinopyranoside and pNP-β-L-mannopyranoside respectively, and both hydrolysed pNP-β-D-glucopyranoside. Conclusion All three AFases displayed different biochemical characteristics despite all showing conserved overall structural similarity with typical domains of AFases belonging to GH51 family. The hydrolysis of cellobiose by a GH51 family AFase is demonstrated for the first time in this study

Effectiveness of systemic family therapy versus treatment as usual for young people after self-harm: a pragmatic, phase 3, multicentre, randomised controlled trial

Background: Self-harm in adolescents is common and repetition occurs in a high proportion of these cases. Scarce evidence exists for effectiveness of interventions to reduce self-harm. Methods: This pragmatic, multicentre, randomised, controlled trial of family therapy versus treatment as usual was done at 40 UK Child and Adolescent Mental Health Services (CAMHS) centres. We recruited young people aged 11–17 years who had self-harmed at least twice and presented to CAMHS after self-harm. Participants were randomly assigned (1:1) to receive manualised family therapy delivered by trained and supervised family therapists or treatment as usual by local CAMHS. Participants and therapists were aware of treatment allocation; researchers were masked. The primary outcome was hospital attendance for repetition of self-harm in the 18 months after group assignment. Primary and safety analyses were done in the intention-to-treat population. The trial is registered at the ISRCTN registry, number ISRCTN59793150. Findings: Between Nov 23, 2009, and Dec 31, 2013, 3554 young people were screened and 832 eligible young people consented to participation and were randomly assigned to receive family therapy (n=415) or treatment as usual (n=417). Primary outcome data were available for 795 (96%) participants. Numbers of hospital attendances for repeat self-harm events were not significantly different between the groups (118 [28%] in the family therapy group vs 103 [25%] in the treatment as usual group; hazard ratio 1·14 [95% CI 0·87–1·49] p=0·33). Similar numbers of adverse events occurred in both groups (787 in the family therapy group vs 847 in the treatment as usual group). Interpretation: For adolescents referred to CAMHS after self-harm, having self-harmed at least once before, our family therapy intervention conferred no benefits over treatment as usual in reducing subsequent hospital attendance for self-harm. Clinicians are therefore still unable to recommend a clear, evidence-based intervention to reduce repeated self-harm in adolescents

This Corrosion: A systematic Review of the Association between Alternative Subcultures and the Risk of Self-Harm and Suicide

Background: Rates of self-harm and suicide are increasing in young people. The literature suggests that individuals who identify with alternative subcultures (e.g. Goth) may be at a greater risk. Objective: To explore the prevalence of self-harm and suicide in alternative subcultures and the factors that might contribute to this increased risk. Method: Using a systematic strategy, the databases PsycINFO, Scopus, MEDLINE and Web of Science and the E-Thesis online service (ETHOS) were searched for English language only papers, with no restrictions in terms of date of publication. Papers were selected that included data on the relationship between either alternative subculture identity (e.g. Goth) or preference for alternative music (e.g. Heavy Metal) and self-harm or suicide. Ten quantitative papers were included; seven cross-sectional, two longitudinal and one cross-sectional state level comparison study. Two qualitative papers were also included. Studies were assessed by two reviewers for risk of bias Results: The findings indicated that individuals who associated with alternative subcultures were at a greater risk of self-harm and suicide. Whilst qualitative papers identified potential mechanisms (e.g. exposure to self-harm and the way self-harm is presented or normalised) there remains limited support for these mechanisms. Conclusions: More research is required to understand the association between self-harm, suicide and alternative subculture affiliation, and the factors underlying it. Longitudinal studies and studies focusing on mechanism are particularly important

Could a brief assessment of negative emotions and self-esteem identify adolescents at current and future risk of self-harm in the community? A prospective cohort analysis

Background: Self-harm is common in adolescents, but it is often unreported and undetected. Available screening tools typically ask directly about self-harm and suicidal ideation. Although in an ideal world, direct enquiry and open discussion around self-harm would be advocated, non-psychiatric professionals in community settings are often reluctant to ask about this directly and disclosure can be met with feeling of intense anxiety. Training non-specialist staff to directly ask about self-harm has limited effects suggesting that alternative approaches are required. This study investigated whether a targeted analysis of negative emotions and self-esteem could identify young adolescents at risk of self-harm in community settings. Methods: Data were collected as part of a clinical trial from young people in school years 8–11 (aged 12–16) at eight UK secondary schools (N = 4503 at baseline, N = 3263 in prospective analysis). The Short Mood and Feelings Questionnaire, Revised Child Anxiety and Depression Scale, Rosenberg Self-Esteem Scale, personal failure (Children’s Automatic Thoughts Scale), and two items on self-harm were completed at baseline, 6 and 12 months. Results: Following a process of Principal Components Analysis, item reduction, and logistic regression analysis, three internally reliable factors were identified from the original measures that were independently associated with current and future self-harm; personal failure (3 items), physical symptoms of depression/anxiety (6 items), positive self-esteem (5 items). The summed score of these 14 items had good accuracy in identifying current self-harm (AUC 0.87 girls, 0.81 boys) and at six months for girls (0.81), and fair accuracy at six months for boys (AUC 0.74) and 12 months for girls (AUC 0.77). Conclusions: A brief and targeted assessment of negative emotions and self-esteem, focusing on factors that are strongly associated with current and future self-harm, could potentially be used to help identify adolescents who are at risk in community settings. Further research should assess the psychometric properties of the items identified and test this approach in more diverse community contexts