Production of Bacterial Cellulose Using Low-cost Media

Bacterial cellulose (BC) is a polymer of glucose monomers, which has unique properties including high crystallinity and high strength. It has the potential to be used in biomedical applications such as making artificial blood vessels, wound dressings, and in the paper making industry. Unlike cellulose from plant sources, it is not contaminated with non-cellulose compounds, making it a candidate for medical use. The aim of this thesis was to optimize BC production using the Gram negative bacterium Gluconacetobacter xylinus DSM 46604, including identifying cheaper ingredients for the culture media. Initial trials were done on solid media and in shake flasks. Trials were then scaled and done in 3-L and 5-L conventional bioreactors. Three different processing strategies were used in the bioreactors: batch, fed-batch and continuous. The morphology of the BC depended on the growth conditions. Thin sheets were formed in stationary cultures and pellicles were formed in agitated cultures. The scanning electron microscope micrographs showed that BC produced under static culture tends to be more densely packed than when produced in agitated shake flasks. Exploratory trials on agar slants and in agitated shake flasks using glucose, sucrose, and lactose showed that G. xylinus DSM 46604 grew well on glucose and produced BC. However, there was minimal growth on the other two carbohydrates. Further trials with initial glucose concentrations between 40 and 100 g/L were done in shake flasks. Glucose concentration did not affect the BC morphology. The maximum BC concentration of 1.13 g/L was produced using 50 g/L glucose. The BC concentration using 100 g/L glucose was only 0.96 g/L. Shake flask studies with 2 to 9 g/L yeast extract (YE) as a nitrogen source in the media showed the maximum BC concentration of 5.2 g/L was obtained using 5 g/L YE with 50 g/L of glucose. Increasing the YE to 7 or 9 g/L produced only 4.82 and 4.06 g BC/L respectively. The effect of two cheaper nitrogen sources, fish hydrolysate and fish powder prepared from waste fish, were investigated. The highest BC concentration of 0.24 g/L was obtained using 20 g/L fish hydrolysate rather than 5 g/L YE. The BC yield of 0.04 g BC /g carbon substrate used were obtained using 5 g/L YE, 20 g/L fish hydrolysate, or 15 or 20 g/L fish powder. The effectiveness of four combinations of banana peel (as a cheaper carbon source) and glucose were investigated in shake flasks trials. The highest BC concentration of 0.43 g/L was obtained using 10 g/L banana peel extract with 40 g/L glucose. This was similar to the BC concentration produced with 50 g/L glucose (control). Trials using the same combination of banana peel and glucose in a 3-L bioreactor produced 1 g/L BC compared with 2.2 g/L for 50 g/L glucose (control). Shake flask fermentations using 10 to 50 g/L glycerol as the carbon source showed that the highest BC concentration of 1.43 g/L was produced with an initial glycerol of 20 g/L. Trials done in a 3-L bioreactor produced 2.87 g/L of BC, representing a yield of 0.15 g/g carbon substrate used. The effect of aeration and agitation on BC production was studied in 3- and 5-L bioreactors. The optimal agitation was 200 rpm at constant air flow rate of 0.3 volume air per volume culture broth per minute (vvm). This produced 4.0 g/L BC and a yield of 0.06 g/g glucose. The optimal aeration rate at 150 rpm was 1.0 vvm and produced 4.4 g/L BC. Various fermentation strategies were then investigated. The control was batch fermentation on 50 g/L glucose in a 3- or 5-L fermenter. All runs were done at 30OC, 200 rpm and 1 vvm aeration. The BC yield when G. xylinus DSM 46604 was grown on 50 g/L glucose using a fill-and-draw fed-batch strategy was 0.05 g/g glucose or glycerol used, which was similar to the control. The BC yield increased to 0.11 g/g when using a pulse-feed fed-batch strategy but the BC yield in continuous fed-batch was only 0.03 g/g. It increased under continuous fermentation conditions and the highest yield (0.13 g/g) was achieved at a dilution rate of 0.1 h⁻¹. If dilution rate was increased further, yields began to decrease. Trials were done by replacing 50 g/L glucose with 20 g/L glycerol. Again, BC yields were higher under continuous conditions than batch fermentation. The BC yield on 20 g/L using a fill-and-draw fed-batch strategy was 0.2 g/g BC compared with 0.15 g/g for the control. This increased to 0.39 g/g for a pulse-feed fed-batch strategy. The BC yield for continuous fed-batch at a dilution rate of 0.1 h⁻¹ was 0.3 g/g. The highest BC yield under continuous conditions was 0.33 g/g when dilution rate was 0.1 h⁻¹. These studies showed that cheaper ingredients such as fish powder or hydrolysate and banana peel extract could partially replace conventional nitrogen and carbon sources such as YE and glucose without affecting BC yield. The BC production was enhanced using fed-batch and continuous processing strategies. Higher BC yields than reported by much of the literature could be obtaining ujsing a combination of low-cost media ingredients and the best reactor conditions

Fish powder as a low-cost component in media for producing bacterial cellulose

Some bacteria can produce extracellular bacterial cellulose (BC). This polysaccharide is chemically identical to cellulose produced by plants but has no associated lignin and hemicelluloses. The unique mechanical properties, chemical stability and purity allow BC to be exploited for a range of biomedical applications. However, medium costs limit commercial BC production. The suitability of using fish powder as a low-cost media component for producing BC by submerged culture of Gluconacetobacter xylinus in shake flasks was investigated. Fish powder was made by drying and grinding Koi carp (Cyprinus carpio), a pest fish in New Zealand waterways. Fermentations were done at 30oC in a growth medium containing 50 g/L glucose, the required minerals, and either 5 g/L yeast extract or 15 g/L fish powder, The BC yield on both yeast extract and fish powder was 0.04 g/g glucose, demonstrating fish powder was a suitable low cost ingredient for supplying nitrogen and amino acids in the media

The effect of curing conditions on the strength of masonry blocks incorporating palm oil fuel ash

Palm Oil Fuel Ash (POFA) is a by-product of the palm oil industry that is often disposed at landfills. In oil palm-producing countries such as Malaysia, Indonesia and Thailand, the high amount of POFA waste disposal is undoubtedly an environmental problem that needs to be overcome to contribute towards zero-carbon emissions by 2050. This paper presents the incorporation of POFA as a partial cement replacement in the production of concrete masonry blocks – a common building material in developing countries. In this study, the cement con�tent by weight of a conventional concrete masonry block was replaced incremen�tally at 10% interval until 30% with ground POFA. The specimens were either cured in water or left dry and tested after 28 days of curing for density, compressive strength and water absorption rate based on standard testing requirements. A general observation has been taken note on the superior results of water-cured masonry blocks with up to 20% POFA content. The results of this study is antic�ipated to add value to the present knowledge bank on incorporating waste material into sustainable building material research and development. In general, POFA is a highly potential replacement for cement, but further studies need to be done to ensure consistency in performance and for industrial application

Employed Bacterial Species and Bacterial Cellulose (BC) Applications: The State of Play

Bacterial cellulose (BC) is an uprising bio-polymer produced by various bacterial strains, which is infamous for its prominent biological properties and applications. Receiving ample attention due to those unique properties, various genus and bacterial strains have been used for BC biosynthesis and the studies of its production have been recorded throughout the years. Although a lot of research and implementation has been done on BC, studies in the search for low-cost, effective medium contributing to higher BC yields were still in continuation to this day. This review article overviews the employed bacterial strains and their recent advance, modified, and low-cost medium in the development of BC composites. Special emphasis is placed on the new-novel strains for BC production and BC applications. Compilations of literature were compiled to outline the sources and also findings by previous and recent researchers. It was found that numerous studies have attempted to enhance BC production, which includes the utilization of various bacterial strains to fulfill industrial needs. Hence, this review comprises bacterial genera and species, which are mainly used in the production of BC such as Komagataeibacter, Gluconobacter, Gluconacetobacter, Enterobacter, and Pseudomonas.The recent studies enforced on BC focusing on higher production and the application of BC on an industrial scale will also be reviewed

Ethical antecedents of dysfunctional behaviour in performance measurement and control system

The importance of performance measurement and control system (PMCS) in enhancing the firm profitability and sustainability has certainly been admitted by many, but findings on its effectiveness have been inconclusive with certain dysfunctional behaviours (DB) like budgetary slack, information or measures manipulation, or gaming, have been reported. Hence, a lot has been debated about what actually lead to these DBs.However, the bulk of researches has only concentrated on the technical aspects towards the betterment of the system which is unfortunately not always true.Ironically, though ethics has captured vast attention and has been admitted as bearing great importance in influencing one’s behaviour, it is a great surprise that very few empirical studies had linked ethics to DB in the context of PMCS. Hence this paper will try to propose how ethical antecedents will affect employees’ propensity to engage in DB.Based on reviews of extant literatures, the article first elaborates the DB in the context of PMCS before proceeding to the ethical antecedents, grouped in personal and organizational ethics, believed to influence the occurrence of DB.Propositions on how these factors will influence DB will be discussed based on social learning theory which would lead to the proposed theoretical framework.Practical implications will also be discusse

Technique for Determining the Viability of Acanthamoeba Cysts Treated with a Cysticidal Agent Based on Membrane Integrity

This study presents a straightforward and reliable method for determining the viability of Acanthamoeba cysts. A standard method for determining Acanthamoeba cyst viability in an in vitro cytotoxicity analysis is required to ensure that the double-walled and sturdy cysts are affected by the substance tested. In this study, a new approach was used to determine the cysticidal potential of redox Cleland’s reagent, dithiothreitol (DTT), against Acanthamoeba cysts. This approach constitutes a significant breakthrough, as the cyst form of Acanthamoeba is known for its high resistance to various chemicals and drugs used to treat infections of the central nervous system and eyes caused by Acanthamoeba. Cyst viability was evaluated based on the intensity of the cyst population under fluorescence produced by propidium iodide (PI) dye and measured using an enzyme-linked immunosorbent assay (ELISA) reader at an absorbance of 636 nm. The results were validated using high-content screening (HCS). For analysis, an individual cell was imaged and examined for phenotypic changes in the Acanthamoeba cyst at the cyst population level. Fluorescence intensity of the cysts in each well in a 96-well plate was measured using Image J software. HCS is an automated technique that uses fluorescence microscopy to produce quantitative data

THE USE OF ILLUSTRATION IN BIOCHEMISTRY TEACHING AND LEARNING

Biochemistry is known as a complex course, especially the metabolic pathway topics. The main issue that instigate this initiative is the learners’ difficulty in understanding metabolic pathway topic(s), resulting in uninteresting learning environment. Hence, ‘the metabolic town’ illustration, that depicts three metabolic pathways (glycolysis, Krebs cycle, and electron transport chain) is used as an initiative to revive learners’ enthusiasm, which could breed interest and motivation to study this course. Trials were conducted with 35 students of Crop Science learners from the Faculty of Fisheries and Food Science, Universiti Malaysia Terengganu. Eighty-six percent (86.2%) responded ‘strongly agree’ and 13.8% responded ‘agree’ that the overall learning experience through the use of this illustration has created a positive and fun environment. Additionally, around 79% learners responded ‘strongly agree’ that their knowledge on these topics have improved while 17.2% responded ‘agree’. Nearly 100% of the learners agreed thus establish the connection between the lecture notes and the illustration. Other than that, from an intrinsic aspect, 72.4% of learners firmly agreed that this illustration aided their interest and motivation towards Biochemistry subject; while the other 27.6% agreed. 89.6% who answered strongly agreed showed that they are in favor of the use of illustration for revision while the rest agreed. Consequently, 86.2% of learners strongly agreed that the illustration boosted their understanding and boost their imagination, and the other 13.8% ‘agreed’. This study investigates how an illustration of analogy could improve the learning process.</jats:p