Flocculation phenomenon of a mutant flocculent Saccharomyces cerevisiae strain: Effects of metal ions, sugars, temperature, pH, protein-denaturants and enzyme treatments

The flocculation mechanism of a stable mutant flocculent yeast strainSaccharomyces cerevisiae KRM-1 was quantitatively investigated for potential industrial interest. It was found that the mutant flocculent strain was NewFlo phenotype by means of sugar inhibition test. The flocculation was completely inhibited by treatment with proteinase K, protein-denaturants and carbohydrate modifier. The absence of calcium ions significantly inhibited the flocculation, indicating that Ca2+ was specifically required for flocculation. The flocculation was stable when temperature below 70°C and pH was in the range of 3.0 - 6.0. The flocculation onset of the mutant flocculent strain was in the early stationary growth phase, which coincided with glucose depletion in the batch fermentation for the production of ethanol from kitchen refuse medium. The results are expected to help develop better strategies for the control of mutant flocculent yeast for future large-scale industrial ethanol fermentation

An overview of foodborne illness and food safety in Malaysia

Foodborne disease has been associated with microorganisms like bacteria, fungi, viruses and parasites. Most commonly, the outbreaks take place due to the ingestion of pathogenic bacteria like Salmonella Typhi, Escherichia coli, Staphylococcus aureus, Vibrio cholera, Campylobacter jejuni, and Listeria monocytogenes. The disease usually happens as a result of toxin secretion of the microorganisms in the intestinal tract of the infected person. Usually, the level of hygiene in the food premises reflect the quality of the food item, hence restaurant or stall with poor sanitary condition is said to be the contributor to food poisoning outbreak. In Malaysia, food poisoning cases are not rare because the hot and humid climate of this country is very suitable for the growth of the foodborne bacteria. The government is also implementing strict rules to ensure workers and owners of food premises prioritize the cleanliness of their working area. Training programme for food handlers can also help them to implement hygiene as a routine in a daily basis. A lot of studies have been done to reduce foodborne diseases. The results can give information about the types of microorganisms, and other components that affect their growth. The result is crucial to determine how the spread of foodborne bacteria can be controlled safely and the outbreak can be reduced

Selective Proliferation of Lactic Acid Bacteria and Accumulation of Lactic Acid during Open Fermentation of Kitchen Refuse with Intermittent pH Adjustment

When minced and autoclaved model kitchen refuse was inoculated with a small amount of non-autoclaved model kitchen refuse as seed culture, incubated at 37°C for 3-5 days and intermittently pH neutralized, 27-45 g/l of lactic acid was accumulated with a small amount of acetic acid and ethanol. The highest accumulation and highest productivity levels of lactic acid were observed at an initial and adjusted pH of 7.0 and a 6 h interval of pH adjustment. After several hours of lag, the lactic acid bacteria became the dominant cell type during the incubation, while the number of coliform bacteria and clostridia decreased. Such selective and stable accumulation of lactic acid was achieved in dozens of different experiments with various refuse preparations. In contrast, with continuous pH adjustment, Iactic acid once accumulated was labile and a small amount of butyric acid was produced, increasing the number of clostridia. The dominant bacteria isolated from the fermentation with intermittent pH adjustment were identified as Lactobacillus plantarnm and L. brevis

Photoluminescence Enhancement of β-FeSi2 Nanocrystals Controlled by Transport of Holes in Cu-doped n-type Si Substrates

We have investigated PL behavior of β-FeSi2 nanocrystals controlled by transport of holes in Cu-doped n-type Si substrates. PL enhancement was observed and PCI-PL measurements revealed that PL enhancement was attributed to a transport process of holes with a larger time constant in Cu-doped n-Si substrate in which an interval trap process is controlled by Cu doping.International Conference and Summer School on Advanced Silicide Technology 2014, July 19–21, 2014, Tokyo, Japa

Bacterial community shift as potential bioindicator for monitoring the performance of palm oil mill effluent treatment system

The growing demand for palm oil has caused a substantial increase in the generation of palm oil mill effluent (POME). POME has been known to give the adverse environmental impacts including land and aquatic ecosystem contamination and the biodiversity loss if it is not properly treated. In Malaysia, the biological ponding system is commonly being used to treat POME because of the low cost and less maintenance is required. However, the current wastewater treatment system for POME regularly fails to treat the effluent efficiently. To meet the standard discharge limit proposed by the Malaysian Department of the Environment, the POME must be treated effectively before being released into the receiving water bodies, hence monitoring a correct operation of POME treatment system is crucial. However, to date, only few studies have been conducted on the microbial aspects of POME and little is known about microbial diversity involved in the POME treatment system, either in terms of their community structure and function or their response to the environment. Therefore, the study on the microbial community composition of POME treatment system has been carried out which later can be used as potential bioindicator to monitor the performance of the treatment system. Sampling from POME treatment system was done by collecting samples from raw POME, anaerobic tanks, as well as from facultative and algae ponds. The shift of microbial community composition at each stage of POME treatment system has been shown by using PCR-Denaturing Gradient Gel Electrophoresis (DGGE) and Illumina Miseq. As a conclusion, a sensitive and accurate monitoring approach of POME treatment system using bacterial community shift is proposed to ensure a correct operation for POME treatment, hence can be used to complement the current physicochemical assessment method

Bacterial community shift as potential bioindicator to indicate the river water contamination due to palm oil mill effluent final discharge

A thorough outlook on the effect of palm oil mill effluent (POME) final discharge towards the composition and functional status of bacterial community in the receiving river is provided in this study by using high-throughput MiSeq and flow cytometry, respectively. The shift of bacterial community dynamics could be used to determine the potential bacterial indicators to indicate contamination caused by POME. This study showed that the POME final discharge did not only alter the natural physicochemical properties of the river water but also caused the reduction of bacterial diversity in the receiving river. The Chromatiaceae and Alcaligenaceae which were not detected in the upstream but were detected in the downstream part of the river are proposed as the indicator bacteria to indicate the river water contamination caused by POME final discharge. The emergence of the potential indicator bacteria in the downstream part of the river was shown to be carried over by the effluent. Moreover, the functional status of the bacterial community at single-cell level is determined with regards to their abundance, viability and nucleic acid content to monitor the effect of POME final discharge in the affected river. The shift of low nucleic acid (LNA) to high nucleic acid (HNA) bacterial cells in the affected river suggests the transformation of dormant to active cells due to POME final discharge which may serves as potential bioindicator in the screening of anthropogenic effect due to POME final discharge in the river water with originally high LNA proportions. Monitoring the effluent discharge at low trophic level using MiSeq and flow cytometry is considered as an accurate pollution monitoring approach which can be used to complement the conventional POME pollution assessment method