Darwin Lyew

Radio-frequency treatment for ready-to-eat fresh carrots

This study was conducted to determine the potential of an RF thermal treatment to improve and extend the storability of vacuum-packaged carrot sticks stored at 5–6C. The results have shown that it is possible to treat carrot sticks to 60C in less than 2 min in a parallel plate RF applicator, and thus reduce the initial total microbial load. The RF treatments were compared to chlorinated water dipping, and hot water dipping. All storage trials of 7–14 days at 6C, have indicated that the reduction of the initial microbial load alone does not maintain the quality of carrot sticks for 14 days, since at this point the microbial loads in all cases studied were higher than 310 6 . Nonetheless, the quality of the RF treated samples was greater than for either the control samples (chlorinated water) or hot-water-treated carrot samples. The RF-treatments maintained colour, taste and the vacuum of the packages, which was not the case for control and hot-water-treated carrots. # 2001 Elsevier Science Ltd. All rights reserved.

Effects of physical parameters of a gravel bed on the activity of sulphate‐reducing bacteria in the presence of acid mine drainage

The use of sulphate-reducing bacteria (SRB) in the passive treatment of acid mine drainage (AMD) requires the presence of a sediment, such as gravel bed, in which the bacteria can establish microenvironments conducive to their survival in the presence of oxygen and acidity. The characterization of relationships between the physical environment and SRB activity would be useful in the sizing of passive treatment systems using SRB. The effects of physical parameters of a gravel bed (i.e. void volume, total surface area of gravel, type of gravel) on SRB activity while in the presence of varying loads of fresh AMD was investigated. SRB activity was expressed as the proportion of sulphate removed after 7 days. The study was accomplished in a series of column reactors containing beds comprising different types and size classes of gravel. SRB were established in the beds and metal and sulphate removal were monitored. Quantifiable relationships were found to exist between SRB activity and the physical parameters of the bed. ©1997 SCI

Carbon neutral electricity production by Synechocystis sp. PCC6803 in a microbial fuel cell

The aim of this work was to illustrate the use of photosynthetic microbes in a microbial fuel cell to produce electricity without the requirement of an external carbon source. This research here describes the use of a cyanobacterium Synechocystis PCC6803, to produce electricity without any net CO(2) production in a two-chambered MFC. Conditions for optimum electricity production were determined through standardizing operating parameters. A maximum power density of 6.7mWm(-3)(anode chamber volume) was achieved under high intensity lighting (10,000lux). Light intensity and wavelength directly affected electricity production, indicating the pivotal role played by photosynthesis. The maximum removal of CO(2) was 625mmolm(-3) over 20h under high intensity light. The results presented here will contribute to the understanding of how cyanobacteria can be exploited for the direct conversion of CO(2) to electric current.

Changes in volatile production during an infection of potatoes by Erwinia carotovora

Abstract The monitoring of volatiles produced by diseased potatoes has been studied as a method of detecting infections in potato storage units. Previous studies attempted to identify pathogen-specific volatiles as markers for the presence of disease, however, consistent results were difficult to obtain. A possible solution is to consider overall qualitative and quantitative changes in the volatile profile over the course of an infection. The objective of this study was to investigate this method of data analysis. The study was done using 1-kg batches of potatoes stored at room temperature in metal canisters fitted with volatile traps containing Chromosorb 105. Either one or all of the potatoes in the batch were inoculated with Erwinia carotovora , the causative agent of soft rot. A canister containing uninoculated healthy potatoes was used as the control. A dynamic headspace sampling method was used to sample periodically the air for volatiles in the experimental and control canisters. The analysis of volatiles was done by gas chromatography. Comparison of the volatile profiles arranged in chronological order showed a progression over time, in the types and amounts of volatiles produced. A wider range of volatiles were produced by infected potatoes than by healthy potatoes. Differences between the volatile profiles of healthy and inoculated potatoes were observed as early as 24 h into the experiment while the total quantity of volatiles produced was initially low and increased exponentially as the infection became well established. The time difference between these two observations was 36–48 h and represented the time in which measures can be taken to contain the infection. The amount of volatile produced was dependent on the initial amount of bacteria, the growth of the bacteria and the detection limits of the Chromosorb and the gas chromatograph.

Energy recovery from cassava peels in a single-chamber microbial fuel cell

ABSTRACT In a number of energy-poor nations, cassava peels represent one of the most abundant forms of lignocellulosic biomass available, and thus present an opportunity for use in microbial fuel cells (MFCs). In an MFC with optimized electrode spacing, biomass produced a power density of 29 mW⋅m–3 in a single-chamber air cathode MFC. This work which examines a way to reduce environmental degradation caused by indiscriminate disposal of organic waste also confirmed the presence of naturally occurring electrogenic organism which can be exploited to recover energy as well as supplement energy production in the growing regions.