title: Two thermostable hemicellulases and their effects on wood pulps

authors: Bicho, Paul A.

abstract: Two hemicellulases, cloned from a thermophilic anaerobe (isolate TP8 6.3.3.1) were partially purified and characterised. The ability of these enzymes to hydrolyse the hemicellulose components of various types of pulps and their effects on the bleachability of radiata pine kraft pulp were examined. The xylanase (two preparations) and mannanase had broad pH optima (6-7.5). The xylanases had temperature optima of 70°C (10 min assay) and the mannanase had an optimum of 80°C (10 min assay). All the cloned enzymes were thermostable with more than 95% of the enzyme activity remaining after 24 hours at 70°C, in an unbuffered solution. Buffering affected the thermostability of the enzymes. The mannanase had a half life of 48 min at 85°C. The xylanases were able to hydrolyse xylans but also had a pH-dependent CM cellulase activity, but this was never more than 10% of the xylanase activity. The mannanase hydrolysed mannan, glucomannans and galactomannans. The glucose content of the glucomannans had little or no effect on mannanase activity but the galactose substituents of the galactomannans severely inhibited the hydrolysis of these substrates.

The thermostable xylanase hydrolysed more than 75% of soluble radiata pine xylan to low molecular weight (< DP10) xylo-oligomers. These included; xylose, xylobiose, xylotriose, arabinose-substituted xylobiose and xylotriose and 4-O-methyl glucuronic acid substituted xylotrioses. The arabinose substituents were bound to the terminal, non-reducing xylose residue; the glucuronic acid substituents may be bound to the non-reducing or central xylose residues of the substituted xylotriose. The thermostable mannanase also hydrolysed more than 75% of soluble radiata glucomannan, producing mannose, mannobiose, mannotriose, glucomannose and glucomannobiose.

The hemicellulases were used to treat (at 70°C, 24 hr) a variety of wood pulps, including kraft (softwood and hardwood), radiata NSAQ pulp, radiata CTMP and radiata TMP. Both enzymes solubilised their respective substrates from these pulps. The chemical pulps were more susceptible to enzymatic attack than the mechanical pulps, possibly due to the greater fibre porosity of the chemical pulps. The xylanase solubilised ~4% of the xylan and the mannanase solubilised 10% of the glucomannan from radiata kraft pulp. In comparison with other xylanases, the thermostable xylanase was less effective in solubilising xylan from kraft pulps. The hemicelluloses of kraft pulps that had been enzyme treated were extracted. The extracted xylan from the xylanase-treated pulp was lower in average DP than the xylan extracted from untreated pulps. The average DP of the extracted glucomannan from the mannanase-treated pulps was no different than that of glucomannans extracted from untreated pulps. The extracted xylan and glucomannan from untreated kraft pulps were readily hydrolysed by the xylanase and the mannanase respectively, suggesting that enzyme inaccessibility to the substrate within the fibre wall was the main cause of their resistance to enzymatic attack.

The effect of these enzymes on the bleachability of radiata kraft pulps was studied by measuring the reduction in kappa number (κ), relative to untreated controls, after a standard D/C E prebleaching sequence. The xylanase and the mannanase had little or no effect on the bleachability of radiata kraft pulps. Xylanase treated kraft pulp required a protease treatment after the hemicellulose treatment but before bleaching, in order to elicit any improvement in bleachability (~7% drop in κ relative to untreated control pulps). Mannanase treated kraft pulp showed no improvement in bleachability. For comparison commercial xylanases (including a thermostable xylanase) were used to treat radiata kraft pulps and did improve bleachability significantly. These enzymes also solubilised three to four times more xylan than the cloned, thermostable xylanase. Therefore, the ineffectiveness of the cloned xylanase may be due to its very limited ability to hydrolyse intra-fibril xylan in kraft pulp fibres.

text: Two thermostable hemicellulases and their effects on wood pulps Two hemicellulases, cloned from a thermophilic anaerobe (isolate TP8 6.3.3.1) were partially purified and characterised. The ability of these enzymes to hydrolyse the hemicellulose components of various types of pulps and their effects on the bleachability of radiata pine kraft pulp were examined. The xylanase (two preparations) and mannanase had broad pH optima (6-7.5). The xylanases had temperature optima of 70°C (10 min assay) and the mannanase had an optimum of 80°C (10 min assay). All the cloned enzymes were thermostable with more than 95% of the enzyme activity remaining after 24 hours at 70°C, in an unbuffered solution. Buffering affected the thermostability of the enzymes. The mannanase had a half life of 48 min at 85°C. The xylanases were able to hydrolyse xylans but also had a pH-dependent CM cellulase activity, but this was never more than 10% of the xylanase activity. The mannanase hydrolysed mannan, glucomannans and galactomannans. The glucose content of the glucomannans had little or no effect on mannanase activity but the galactose substituents of the galactomannans severely inhibited the hydrolysis of these substrates.

The thermostable xylanase hydrolysed more than 75% of soluble radiata pine xylan to low molecular weight (< DP10) xylo-oligomers. These included; xylose, xylobiose, xylotriose, arabinose-substituted xylobiose and xylotriose and 4-O-methyl glucuronic acid substituted xylotrioses. The arabinose substituents were bound to the terminal, non-reducing xylose residue; the glucuronic acid substituents may be bound to the non-reducing or central xylose residues of the substituted xylotriose. The thermostable mannanase also hydrolysed more than 75% of soluble radiata glucomannan, producing mannose, mannobiose, mannotriose, glucomannose and glucomannobiose.

The hemicellulases were used to treat (at 70°C, 24 hr) a variety of wood pulps, including kraft (softwood and hardwood), radiata NSAQ pulp, radiata CTMP and radiata TMP. Both enzymes solubilised their respective substrates from these pulps. The chemical pulps were more susceptible to enzymatic attack than the mechanical pulps, possibly due to the greater fibre porosity of the chemical pulps. The xylanase solubilised ~4% of the xylan and the mannanase solubilised 10% of the glucomannan from radiata kraft pulp. In comparison with other xylanases, the thermostable xylanase was less effective in solubilising xylan from kraft pulps. The hemicelluloses of kraft pulps that had been enzyme treated were extracted. The extracted xylan from the xylanase-treated pulp was lower in average DP than the xylan extracted from untreated pulps. The average DP of the extracted glucomannan from the mannanase-treated pulps was no different than that of glucomannans extracted from untreated pulps. The extracted xylan and glucomannan from untreated kraft pulps were readily hydrolysed by the xylanase and the mannanase respectively, suggesting that enzyme inaccessibility to the substrate within the fibre wall was the main cause of their resistance to enzymatic attack.

The effect of these enzymes on the bleachability of radiata kraft pulps was studied by measuring the reduction in kappa number (κ), relative to untreated controls, after a standard D/C E prebleaching sequence. The xylanase and the mannanase had little or no effect on the bleachability of radiata kraft pulps. Xylanase treated kraft pulp required a protease treatment after the hemicellulose treatment but before bleaching, in order to elicit any improvement in bleachability (~7% drop in κ relative to untreated control pulps). Mannanase treated kraft pulp showed no improvement in bleachability. For comparison commercial xylanases (including a thermostable xylanase) were used to treat radiata kraft pulps and did improve bleachability significantly. These enzymes also solubilised three to four times more xylan than the cloned, thermostable xylanase. Therefore, the ineffectiveness of the cloned xylanase may be due to its very limited ability to hydrolyse intra-fibril xylan in kraft pulp fibres.

year: 1992

title: The ‘frontal lobe’ project: A double-blind, randomized controlled study of the effectiveness of higher level driving skills training to improve frontal lobe (executive) function related driving performance in young drivers

authors: Isler, Robert B.

subjects: psychology

abstract: The current study was undertaken in order to evaluate the effectiveness of higher level skills training on safe driving behaviour of 36 teenage drivers. The participants, who attended the Driver Training Research camp in Taupo (NZ) over a two week period, were 16 to 17 years old and had a valid restricted driver licence. The study focused on four main aims. Firstly, the behavioural characteristics of the sample and their attitudes to risk taking and driving were examined. Results showed that speeding was the most anticipated driving violation, and high levels of confidence were associated with a higher number of crashes and a greater propensity for risk taking. Many, often male participants, also rated their driving skills as superior to others and thought they would be less likely than others to be involved in an accident. Secondly, the relationship between driving performance and executive functioning, general ability and sustained attention was evaluated. Overall, better driving performance and more accurate self-evaluation of driving performance was related to higher levels of executive functions, in particular, working memory, and
cognitive switching. In addition, higher general ability and greater ability to sustain attention were also linked to better performance on the driving related assessments.  The third focus of this study was to compare the effects of both, higher level and vehicle handling skills training on driving performance, confidence levels and
attitudes to risk. While both types of training improved direction control, speed
choice and visual search, along with number of hazards detected and actions in relation to hazards, statistically significant improvement on visual search was seen only after higher level skills training. Vehicle handling skills training significantly improved direction control and speed choice. In addition, confidence levels in their driving skills were significantly lowered and attitudes to speeding, overtaking and
close following had improved significantly in the participants after the higher level
driving skills training. The final aspect to this study was to examine the effects of the
training over the following 6 month period based on self-reported driving behaviour.
The response rate of participants however, was not sufficient to reach any meaningful conclusion on any long-term training effects. A pilot study using GPSbased data trackers to assess post-training driving behaviour revealed some promising results for future driver training evaluation studies. The overall implications of the results are discussed in relation to improving the safety of young 
drivers in New Zealand.

text: The ‘frontal lobe’ project: A double-blind, randomized controlled study of the effectiveness of higher level driving skills training to improve frontal lobe (executive) function related driving performance in young drivers The current study was undertaken in order to evaluate the effectiveness of higher level skills training on safe driving behaviour of 36 teenage drivers. The participants, who attended the Driver Training Research camp in Taupo (NZ) over a two week period, were 16 to 17 years old and had a valid restricted driver licence. The study focused on four main aims. Firstly, the behavioural characteristics of the sample and their attitudes to risk taking and driving were examined. Results showed that speeding was the most anticipated driving violation, and high levels of confidence were associated with a higher number of crashes and a greater propensity for risk taking. Many, often male participants, also rated their driving skills as superior to others and thought they would be less likely than others to be involved in an accident. Secondly, the relationship between driving performance and executive functioning, general ability and sustained attention was evaluated. Overall, better driving performance and more accurate self-evaluation of driving performance was related to higher levels of executive functions, in particular, working memory, and
cognitive switching. In addition, higher general ability and greater ability to sustain attention were also linked to better performance on the driving related assessments.  The third focus of this study was to compare the effects of both, higher level and vehicle handling skills training on driving performance, confidence levels and
attitudes to risk. While both types of training improved direction control, speed
choice and visual search, along with number of hazards detected and actions in relation to hazards, statistically significant improvement on visual search was seen only after higher level skills training. Vehicle handling skills training significantly improved direction control and speed choice. In addition, confidence levels in their driving skills were significantly lowered and attitudes to speeding, overtaking and
close following had improved significantly in the participants after the higher level
driving skills training. The final aspect to this study was to examine the effects of the
training over the following 6 month period based on self-reported driving behaviour.
The response rate of participants however, was not sufficient to reach any meaningful conclusion on any long-term training effects. A pilot study using GPSbased data trackers to assess post-training driving behaviour revealed some promising results for future driver training evaluation studies. The overall implications of the results are discussed in relation to improving the safety of young 
drivers in New Zealand.

year: 2008-06

title: Academic success amongst a cohort of gifted and talented Māori and Pasifika secondary school boys: Elements that have contributed to their achievement

authors: Miller, Graeme Oliver

subjects: Māori

abstract: In recent years Māori and Pasifika students have been the focus of much discussion and a significant amount of research relating to underachievement. Despite this, many Māori and Pasifika secondary school boys are achieving highly in the academic sphere within the context of mainstream boys’ state secondary schools in New Zealand. Achievement aside, evidence shows that Māori and Pasifika secondary school boys are seriously under-represented in programmes for the gifted and talented. This enquiry examines factors in relation to identifying gifted and talented students, and investigates how their abilities are forged and nurtured. The reasons for student success merit serious investigation because of how the multiple elements contributing to their achievement are likely to be applicable to others, and are a pressing concern for academic attainment in the New Zealand education system. 
 
This qualitative study examines why 30 academically successful Māori and Pasifika secondary school boys achieved highly in the mainstream education system. The boys ranged from 13 to 19 years, the youngest being in his first year at high school as a Year 9 student, and the oldest being in his second year at university. The thesis argues their academic success was due to the complex interplay of home and school environmental elements, and the boys’ intrapersonal characteristics. The study explored the boys’ and parents’ narratives to explain why students had achieved highly, and examined both the parents’ and boys’ perceptions of how well the schools had provided for their intellectual, emotional and cultural needs. Sociocultural learning theory is the main theoretical lens through which the findings are viewed. The methodology is primarily built upon narrative inquiry. The main method of data collection was by semi-structured interview, both individually and in focus groups. Supplementary methods utilised were questionnaires and observation.  
  
An issue in the research was the disparity between the cultural and ethnic background of the participants and myself as the researcher. However, an endeavour was made to mitigate this by consulting with Māori and Pasifika educators, a kaumatua (elder) and iwi (tribal) representative prior to the research commencing. In addition, models developed through this study were submitted to Māori and Pasifika educators for their comment and approval prior to being included. 
 
With its focus specifically on highly-achieving Māori and Pasifika secondary school boys, this thesis makes an original contribution to the national and international discussion about raising student achievement. It provides a platform for further research to 	address the particular concerns around the underachievement of Māori and Pasifika secondary school boys. 
 
While there are several implications arising from the research, all are linked to the need for policy makers and educators to address the issue of the underrepresentation of Māori and Pasifika students in programmes for the gifted and talented. Policies, practices and relationships need to be examined to evaluate how effectively they contribute to gifted and talented Māori and Pasifika students receiving the academic opportunities they deserve. A key part of this examination will need to include consultation with students and their whānau.

text: Academic success amongst a cohort of gifted and talented Māori and Pasifika secondary school boys: Elements that have contributed to their achievement In recent years Māori and Pasifika students have been the focus of much discussion and a significant amount of research relating to underachievement. Despite this, many Māori and Pasifika secondary school boys are achieving highly in the academic sphere within the context of mainstream boys’ state secondary schools in New Zealand. Achievement aside, evidence shows that Māori and Pasifika secondary school boys are seriously under-represented in programmes for the gifted and talented. This enquiry examines factors in relation to identifying gifted and talented students, and investigates how their abilities are forged and nurtured. The reasons for student success merit serious investigation because of how the multiple elements contributing to their achievement are likely to be applicable to others, and are a pressing concern for academic attainment in the New Zealand education system. 
 
This qualitative study examines why 30 academically successful Māori and Pasifika secondary school boys achieved highly in the mainstream education system. The boys ranged from 13 to 19 years, the youngest being in his first year at high school as a Year 9 student, and the oldest being in his second year at university. The thesis argues their academic success was due to the complex interplay of home and school environmental elements, and the boys’ intrapersonal characteristics. The study explored the boys’ and parents’ narratives to explain why students had achieved highly, and examined both the parents’ and boys’ perceptions of how well the schools had provided for their intellectual, emotional and cultural needs. Sociocultural learning theory is the main theoretical lens through which the findings are viewed. The methodology is primarily built upon narrative inquiry. The main method of data collection was by semi-structured interview, both individually and in focus groups. Supplementary methods utilised were questionnaires and observation.  
  
An issue in the research was the disparity between the cultural and ethnic background of the participants and myself as the researcher. However, an endeavour was made to mitigate this by consulting with Māori and Pasifika educators, a kaumatua (elder) and iwi (tribal) representative prior to the research commencing. In addition, models developed through this study were submitted to Māori and Pasifika educators for their comment and approval prior to being included. 
 
With its focus specifically on highly-achieving Māori and Pasifika secondary school boys, this thesis makes an original contribution to the national and international discussion about raising student achievement. It provides a platform for further research to 	address the particular concerns around the underachievement of Māori and Pasifika secondary school boys. 
 
While there are several implications arising from the research, all are linked to the need for policy makers and educators to address the issue of the underrepresentation of Māori and Pasifika students in programmes for the gifted and talented. Policies, practices and relationships need to be examined to evaluate how effectively they contribute to gifted and talented Māori and Pasifika students receiving the academic opportunities they deserve. A key part of this examination will need to include consultation with students and their whānau.

year: 2015