title: Studies on soil and microbial lipases

authors: Cooper, Alvin Bryce

abstract: The relative sensitivities of four methods for the determination of lipase activity was found to be dependent upon the source of the enzyme, when comparisons were made using commercial porcine pancreatic lipase and two partially-purified bacterial lipases. 

Lipase activity was dependent upon substrate surface area rather than substrate concentration per se. Long-chain insoluble fatty acids were inhibitory to lipase activity. A minimum concentration of fatty acid was required before inhibition of lipase activity occurred. This minimum inhibitory concentration was inversely related to the chain length of the fatty acid. Fatty acid inhibition of lipase activity could be partially reversed by the addition of Ca²⁺. 

A sensitive and precise assay for the determination of soil lipase activity was developed. The assay involves a 3h 0.1 M tetra-sodium pyrophosphate (pH 7.5) extraction of soil, followed by a 10 min. assay on the extract using the fluorogenic substrate 4-methyl umbelliferone nonanoate (4 MUN). Basal lipase activities of thirteen New Zealand topsoils ranged from 28 to 597 nmol 4-methyl umbelliferone (4 MU) produced min⁻¹ g⁻¹ of oven-dried soil and were not strongly correlated with soil pH, clay content, cation-exchange capacity, or organic matter. 

The addition of triacylglycerols to soil samples induced microbial production of lipase resulting in triacylglycerol degradation and associated oxygen consumption. With tallow applied to a Hamilton clay loam topsoil sample at the rate of 2.5 mg g⁻¹ and incubated at 25°C, lipase levels increased from 160 nmol 4 MU min⁻¹ g⁻¹ to 490 nmol 4 MU min⁻¹ g⁻¹ after 8 days and the majority of the triacylglycerol was degraded within 14 days. The time for significant triacylglycerol degradation to occur was related to the level of lipase induction upon amendment and not upon the basal lipase levels of the soil. The extent of lipase induction and, therefore, triacylglycerol degradation, was influenced by loading rate, type of triacylglycerol, soil type, temperature, and mineral nutrient additions. In synthetic mixtures of substrates the breakdown of triacylglycerol occurred after the microbial oxidation of alternative substrates. 

The lipolytic microbiota of both unamended and triacylglycerol-amended soils were isolated. The bacterial population demonstrated the greatest increase upon amendment with triacylglycerols. A bacterial isolate obtained by enrichment culture, and designated Pseudomonas 017, was capable of producing high levels of extracellular inductive lipase when grown upon triacylglycerols, long-chain fatty acids and hydrocarbons. Growth upon these substrates was accompanied by the production of an emulsifying agent. The lipase of Pseudomonas 017 was partially purified and characterised.

text: Studies on soil and microbial lipases The relative sensitivities of four methods for the determination of lipase activity was found to be dependent upon the source of the enzyme, when comparisons were made using commercial porcine pancreatic lipase and two partially-purified bacterial lipases. 

Lipase activity was dependent upon substrate surface area rather than substrate concentration per se. Long-chain insoluble fatty acids were inhibitory to lipase activity. A minimum concentration of fatty acid was required before inhibition of lipase activity occurred. This minimum inhibitory concentration was inversely related to the chain length of the fatty acid. Fatty acid inhibition of lipase activity could be partially reversed by the addition of Ca²⁺. 

A sensitive and precise assay for the determination of soil lipase activity was developed. The assay involves a 3h 0.1 M tetra-sodium pyrophosphate (pH 7.5) extraction of soil, followed by a 10 min. assay on the extract using the fluorogenic substrate 4-methyl umbelliferone nonanoate (4 MUN). Basal lipase activities of thirteen New Zealand topsoils ranged from 28 to 597 nmol 4-methyl umbelliferone (4 MU) produced min⁻¹ g⁻¹ of oven-dried soil and were not strongly correlated with soil pH, clay content, cation-exchange capacity, or organic matter. 

The addition of triacylglycerols to soil samples induced microbial production of lipase resulting in triacylglycerol degradation and associated oxygen consumption. With tallow applied to a Hamilton clay loam topsoil sample at the rate of 2.5 mg g⁻¹ and incubated at 25°C, lipase levels increased from 160 nmol 4 MU min⁻¹ g⁻¹ to 490 nmol 4 MU min⁻¹ g⁻¹ after 8 days and the majority of the triacylglycerol was degraded within 14 days. The time for significant triacylglycerol degradation to occur was related to the level of lipase induction upon amendment and not upon the basal lipase levels of the soil. The extent of lipase induction and, therefore, triacylglycerol degradation, was influenced by loading rate, type of triacylglycerol, soil type, temperature, and mineral nutrient additions. In synthetic mixtures of substrates the breakdown of triacylglycerol occurred after the microbial oxidation of alternative substrates. 

The lipolytic microbiota of both unamended and triacylglycerol-amended soils were isolated. The bacterial population demonstrated the greatest increase upon amendment with triacylglycerols. A bacterial isolate obtained by enrichment culture, and designated Pseudomonas 017, was capable of producing high levels of extracellular inductive lipase when grown upon triacylglycerols, long-chain fatty acids and hydrocarbons. Growth upon these substrates was accompanied by the production of an emulsifying agent. The lipase of Pseudomonas 017 was partially purified and characterised.

year: 1982

title: Eccentric Force-Velocity Characteristics during a Novel Squat Protocol in Trained Rugby Union Athletes-Pilot Study

authors: McNeill, Conor

subjects: energy absorption

abstract: Eccentric strength characteristics have been shown to be important factors in physical performance. Many eccentric tests have been performed in isolation or with supramaximal loading. The purpose of this study was to investigate within- and between- session reliability of an incremental eccentric back squat protocol. Force plates and a linear position transducer captured force-time-displacement data across six loading conditions, separated by at least seven days. The reliability of eccentric specific measurements was assessed using coefficient of variation (CV), change in mean, and intraclass correlation coefficient (ICC). Eccentric peak force demonstrated good ICC (≥0.82) and TE (≤7.3%) for each load. Variables based on mean data were generally less reliable (e.g., mean rate of force development, mean force, mean velocity). This novel protocol meets acceptable levels of reliability for different eccentric-specific measurements although the extent to which these variables affect dynamic performance requires further research.

text: Eccentric Force-Velocity Characteristics during a Novel Squat Protocol in Trained Rugby Union Athletes-Pilot Study Eccentric strength characteristics have been shown to be important factors in physical performance. Many eccentric tests have been performed in isolation or with supramaximal loading. The purpose of this study was to investigate within- and between- session reliability of an incremental eccentric back squat protocol. Force plates and a linear position transducer captured force-time-displacement data across six loading conditions, separated by at least seven days. The reliability of eccentric specific measurements was assessed using coefficient of variation (CV), change in mean, and intraclass correlation coefficient (ICC). Eccentric peak force demonstrated good ICC (≥0.82) and TE (≤7.3%) for each load. Variables based on mean data were generally less reliable (e.g., mean rate of force development, mean force, mean velocity). This novel protocol meets acceptable levels of reliability for different eccentric-specific measurements although the extent to which these variables affect dynamic performance requires further research.

year: 2021-03-30

title: The Buried Village, New Zealand - an example of dark tourism?

authors: Ryan, Chris

subjects: dark tourism

abstract: In 1886, the explosion of Mount Tarawera resulted in the loss of 150 lives and the burial of the village of Te Wairoa, the base from which tourists had visited the Pink and White Terraces, a silicone-stained natural formation then advertised as one of the natural wonders of the world. Since 1931, the buried site has itself been a tourist attraction and Smith and Croy have argued that it serves as an example of “dark tourism”. This paper uses a different methodology to argue that Lennon and Foley's original definition of dark tourism is precise, that the buried village of Te Wairoa does not meet that specification, but does support the model suggested by Sharpley, that the site's characteristics are those of grey tourism supply. However, the findings derived from a sample of over 600 respondents indicate that sites are complex packages of potential experiences, and are potentially multi-faceted in terms of the experiences they offer. It is also suggested that cultural components might play a role in the experience of what is “dark” about a site.

text: The Buried Village, New Zealand - an example of dark tourism? In 1886, the explosion of Mount Tarawera resulted in the loss of 150 lives and the burial of the village of Te Wairoa, the base from which tourists had visited the Pink and White Terraces, a silicone-stained natural formation then advertised as one of the natural wonders of the world. Since 1931, the buried site has itself been a tourist attraction and Smith and Croy have argued that it serves as an example of “dark tourism”. This paper uses a different methodology to argue that Lennon and Foley's original definition of dark tourism is precise, that the buried village of Te Wairoa does not meet that specification, but does support the model suggested by Sharpley, that the site's characteristics are those of grey tourism supply. However, the findings derived from a sample of over 600 respondents indicate that sites are complex packages of potential experiences, and are potentially multi-faceted in terms of the experiences they offer. It is also suggested that cultural components might play a role in the experience of what is “dark” about a site.

year: 2006