A survey has been made of the occurrence and distribution of three enzymes which metabolize cyanide in a variety of higher plants including both cyanogenic and non-cyanogenic species. The enzymes investigated were β-cyanoalanine synthase, rhodanese and formamide hydrolyase. β-Cyanoalanine synthase was found to be present in every higher plant tested whereas rhodanese was found to occur far less commonly in plants. Formamide hydrolyase activity was not detected in any of the higher plants tested. In addition, quantitative analyses have been made of the potential hydrogen cyanide content of each plant investigated. A general trend was apparent between the hydrogen cyanide potential and cyanide metabolizing activity, in that the higher the hydrogen cyanide potential, in general, the higher the cyanide metabolizing activity.

Metabolism of hydrogen cyanide by higher plants.

Rhizobacteria strains were characterized for ability to synthesize hydrogen cyanide and for effects on seedling root growth of various plants. Approximately 32% of bacteria from a collection of over 2000 isolates were cyanogenic, evolving HCN from trace concentrations to >30 nmoles/mg cellular protein. Cyanogenesis was predominantly associated with pseudomonads and was enhanced when glycine was provided in the culture medium. Concentrations of HCN produced by rhizobacteria were similar to exogenous concentrations inhibiting seedling growth in bioassays, suggesting that cyanogenesis by rhizobacteria in the rhizosphere can adversely affect plant growth. Growth inhibition of lettuce and barnyardgrass by volatile metabolites of the cyanogenic rhizobacteria confirmed that HCN was the major inhibitory compound produced. Our results suggest that HCN produced in the rhizospheres of seedlings by selected rhizobacteria is a potential and environmentally compatible mechanism for biological control of weeds.

Cyanide production by rhizobacteria and potential for suppression of weed seedling growth.

Volatile metabolites from a number of rhizosphere pseudomonads prevented lettuce root growth in a seedling bioassay. One of these metabolites was identified as cyanide. Direct contact between rhizobacteria and plant roots produced, with one exception, similar responses. However, not all cyanogenic isolates were plant-growth-inhibitory rhizobacteria. When grown in liquid culture, cyanogenic strains produced an average of 37 nmol HCN ml−1 over a 36-h period and inhibition of root growth occurred at concentrations as low as 20 nmol ml−1. Cyanogenic strains introduced into sand or soil also produced HCN. Two cyanogenic strains ofPseudomonas fluorescens, one (5241) a plant-growth inhibitory rhizobacterium and the other (S97) a plant-growth-promotory rhizobacterium, were used to treat bean and lettuce seedlings prior to planting in soil. Lettuce dry weight was reduced by 49.2% (day 28) and 37.4% (day 49) when inoculated with S241 whereas S97 increased growth initially (+64.5% at day 28, no difference from control at day 49). Equivalent figures for inoculated bean plants were: −52.9% and −65.1% (5241); +40.7% and +23.3% (S97). A more detailed experiment using only bean plants confirmed these contrasting affects. Inhibition by S241 was related to consistently higher levels of rhizosphere cyanide in comparison with S97-treated plants and control soils. S241 also survived in the rhizosphere at higher densities and for a longer period of time than S97. The possible contribution of rhizobacterial cyanogenesis to plant growth inhibition is discussed.

Cyanide production by rhizobacteria as a possible mechanism of plant growth inhibition

Traditional approaches to the question of the effects of plant secondary metabolites on the feeding choices of folivores of Eucalyptus have focused on the tree species level, although numerous field studies of foraging behaviour have identified selection at the level of the individual trees. Attempts to relate these decisions to deterrency resulting from secondary leaf chemistry have been inconclusive because assays used have focused on broad groups of compounds such as "total" phenolics. In this study we have conducted no-choice feeding trials with two arboreal mammalian folivores, the common ringtail possum (Pseudocheirus peregrinus) and the koala (Phascolarctos cinereus), to measure deterrency of individual trees of two species of Eucalyptus, E. ovata and E. viminalis. Average daily intakes of E. ovata foliage by common ringtail possums ranged from 2.5 to 50 g kg-0.75 body mass. Koala intakes of foliage from the same individual trees ranged from 22.4 to 36.3 g kg-0.75 body mass. When fed foliage from different individual E. viminalis trees, common ringtail possums ate between 1.26 and 6.28 g kg-0.75 body mass while koalas ate from 14.3 to 45.9 g kg-0.75 body mass. Correlative analyses showed no relationships between feeding and several measures of nutritional quality, nor with total phenolics or condensed tannins. They did, however, identify two groups of plant secondary metabolites that may cause deterrency: terpenes, and a defined group of phenolic compounds, the diformylphloroglucinols (DFPs). Further bioassay experiments with common ringtail possums showed that only the DFPs could cause the effects seen with the foliage experiments at concentrations similar to those found in the leaves. We argue that, when in sufficiently high concentrations, DFPs determine the level of food intake by these animals irrespective of other questions of nutritional quality of the leaves.

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Intraspecific variation in Eucalyptus secondary metabolites determines food intake by folivorous marsupials

Chapter 2 – Cyanide and Cyanogenic Glycosides

Stable reagents for the colorimetric determination of cyanide by modified Koenig reactions

Colorimetric determination of sulfate in water with barium violurate.

Colorimetric determination of fluoride with an insoluble inverse basic beryllium-carboxylate dye complex


 Current mud monitoring practices are limited due to their reliance on manual measurements such as funnel viscometers, weight balances, or basic field rheometers. These manual practices impose restraints on the quantity and quality of the available data that are essential to ensure optimal and safe drilling operations. In this study, we introduce a new autonomous mud viscosity/density system based on an electromechanical tuning fork resonator. The system was integrated into an edge-computing system for improved data collection and deployment of machine learning models. The system was tested during a live drilling campaign. The viscosity/density sensor is based on an electromechanical tuning fork resonator. The sensor was integrated into a submergible housing for in-tank measurements. Two systems were developed for simultaneous measurements at inflow (possum belly) and outflow (suction pit). The data from the two systems were broadcast wirelessly to the central computer room at the rig for real-time display and data aggregation by the edge-computing system for the development of time-series analysis models using machine learning. During initial field testing, data from a single sensor were collected for various hours at a rate less than a sample per second. The test allowed for continuous monitoring of the mud consistency not accessible by current measurement practices. The data demonstrated the potential to perform real-time calculation and display of drilling parameters and to detect anomalies in the fluid that might be indicative of developing operational problems, which would enable the instrument to be used as an early-warning system and real-time calculation of drilling parameters. The system detailed here provides an essential building block to enable drilling automation. The robustness and compactness of the instrument allow it to be installed at various points in the mud circulation system for the generation of large data sets that can be processed using modern analytics algorithms in an edge-computing framework.

Autonomous Viscosity/Density Sensing System for Drilling Edge-Computing System


 Oil and gas drilling requires several components work simultaneously to ensure smooth and safe drilling. Drilling fluid or mud is an inseparable part of drilling oil and gas wells and circulated through out theh drilling operation. Drilling fluid contains a variety of additives or chemicals to provide various properties to drilling fluid namely viscosity, fluid loss control, emulsion stability, lubricity, etc. Developing environment friendly chemicals to provide the above-mentioned drilling fluid properties is a significant step taken towards sustainability and reducing carbon footprint besides suitability for aquifers and offshore environments. Several fatty acid-based chemicals used in drilling fluids as fatty acids offer eco-friendly and bio-degradable properties besides required drilling fluid properties. Vegatable oil contains triglycerides which is a potential source of fatty acids and their derivatives. Waste vegetable oil (WVO) provides a perpetual and sustainable source of raw material for various types of eco-friendly additives development. Waste vegetable oil is subjected to simple chemical modification of base hydrolysis process and mixtures of fatty acids have been obtained after finishing a sequence of clean-up process of reaction mixture. The fatty acids obtained are environment-friendly, bio-degradable and non-toxic. Due to technical, economic and environmental advantages of products derived from waste vegetable oils, we have undertaken several research projects to produce various chemicals from waste vegetable oil for oil and gas field applications. Fatty acid-based products mainly used in drilling fluids as lubricants to reduce torque and drag for water-based mud. In case of oil-based mud systems, fatty acid derived products are used as emulsifiers, wetting agents and rheology modifiers. However, these products have been either mixture of fatty acids and their derivatives or only derivatives of fatty acids. In our study, we have used the mixture of fatty acids obtained from chemical conversion of WVO for applications as lubricant for water-based mud and emulsifier and rheology modifier for invert emulsion oil-based mud systems. In this paper, we described the chemicals process for converting waste vegetable oil to fatty acids by base hydrolysis reaction in the first section. Application of synthesized fatty acids for water-based and oil-based mud formulation as lubricants, emulsifiers and rheology modifiers have been discussed in the second part of the paper.

Jothi. Ramasamy

Papers

Stable reagents for the colorimetric determination of cyanide by modified Koenig reactions

Colorimetric determination of sulfate in water with barium violurate.

Colorimetric determination of fluoride with an insoluble inverse basic beryllium-carboxylate dye complex

Autonomous Viscosity/Density Sensing System for Drilling Edge-Computing System

Sustainable and Green Drilling Fluid Additives Development