In addition, it represents my own opinion and not necessarily that of Cape Peninsula University of Technology and its sponsors. It is a tropical perennial of the Euphorbiaceae family whose vegetative propagation takes place by cutting the stem.
INTRODUCTION
- I NTRODUCTION
- H YPOTHESIS AND RESEARCH QUESTIONS
- Hypothesis
- Research questions
- R ESEARCH AIMS AND OBJECTIVES
- S IGNIFICANCE OF THE STUDY
- D ELINEATION OF THE STUDY
The products of this plant are toxic due to its free cyanide (CN-) content and its precursors, such as Linamarin, Lotaustralin, and other cyanogenic glycosides such as 2-((6-O-(β-D-apiofuranosyl)-β - D-glucopyranosyl)oxy)-2-methylbutanenitrile), which is enzymatically transformed into CN- (Prawat et al., 1995; Andersen et al., 2000). These mycotoxins include Ochratoxin A, Fumonisin B1, Pyranonigrin A, TensidolB, Funalenone, Naphtho-y-pyrone and Malformines (Ottesen et al., 2010; Perrone et al., 2011).
LITERATURE REVIEW
- I NTRODUCTION
- C YANOGEN AND MYCOTOXIN REDUCTION
- Biological reduction of cyanogens
- Biological reduction of mycotoxins
- T OXICITY OF CYANIDE AS A CYANOGEN AND MYCOTOXINS FROM CASSAVA
- Toxicity of cassava
- Impact of cyanogens on biochemical and physical properties of agricultural soil
- Production of mycotoxins
- Mycotoxins effects on soil ecology
- Cyanogen and mycotoxin movement behaviour in soil
- C YANOGEN AND MYCOTOXIN EFFECTS ON HUMANS / ANIMALS
- S UMMARY
In general, free cyanide originates from both anthropogenic and natural processes (Dash et al., 2006; Cumbana et al., 2007). As a result of enzymatic hydrolysis, linamarin is transformed into acetone-cyanohydrin in plant tissue (Montagnac et al., 2009).
RESEARCH DESIGN, MATERIALS AND METHODS
- O VERVIEW OF RESEARCH DESIGN AND METHODOLOGY
- Quality of Chemical reagents
- Reliability of Food and Agriculture Organisation (FAO) data
- Model development and HCN projection load into the environment
- Statistical analysis of FAO data
- Cassava plant health studies
- Determination of plant’s chlorophyll content and photosynthetically active radiation (PAR)
- Determination of gases (HCN, NH 3 , NO 2 ) volatilised from cassava plants
- I SOLATION , CHARACTERISATION AND IDENTIFICATION OF A CYANIDE - RESISTANT ORGANISM FROM CASSAVA (M ANIHOT
- Analytical methods: Microbial isolation, characterisation and identification
- S CREENING OF THE CYANIDE - RESISTANT ISOLATE PATHOGENIC ACTIVITY ON THE MICROBIAL COMMUNITIES IN CASSAVA -
- Analytical methods: pathogenic activity assessment
- Proposed mitigation strategy implementation
Quantification of the concentration of gases (HCN, NH3, NO2) released from young cassava plants, as well as determining the contribution of cassava to the global cyanide burden in the atmosphere. Screening of isolates (isolated in Chapter 5) and pathogenic activity on soil microbial communities grown with cassava. The containers were sealed with silicone glue. AC-9906) was placed at the bottom of the gas analyzer.
The mycelium was re-suspended in 350 µL of BF1 solution and transferred to the PowerBiofilm bead tube. BF4 solution (900 µL) was added followed by vortexing; with 650 µL of the supernatant being transferred to a spin filter tube and centrifuged at 13,000 x g for 1 min. This was followed by incubation of the Petri dishes at 37 °C using an incubator (KIMIX-PROLAB instruments, Switzerland) for 72 h in order to facilitate the growth of the soil microbial community.
Nepenthes mirabilis used during this part of the study was donated by Pan's Carnivores Nursery (Tokai, Cape Town).
A DECADE’S (2014–2024) PERSPECTIVE ON CASSAVA’S (MANIHOT ESCULENTA
- I NTRODUCTION
- O BJECTIVES
- M ATERIALS AND M ETHODS ( SUMMARY )
- R ESULTS AND D ISCUSSION
- Cassava production and estimated hydrogen cyanide load into the environment
- Assessment of cassava plant gases (HCN, NH 3 , NO 2 ) volatilised, chlorophyll content and
- S UMMARY
However, the concentration of cyanogenic compounds differs from tubers to leaves, with leaves having a higher cyanogen concentration during the cultivar's early growth stages (Montagnac et al., 2009). Therefore, it is prudent to assess the spatial and temporal distribution of cassava in the environment with the related effects of cyanogen compounds and HCN in particular, because HCN is a pseudo-halogen that is a contributing factor to ozone depletion that may be associated with global warming and consequently climate change (Breton et al., 2013). This suggests that sub-Saharan Africa is the largest region in global cassava production (Jansson et al., 2009; Jarvis et al., 2012).
Recently, cassava production has increased for several reasons: Africa (55%, self-feeding only), Asia (32%, for self-feeding and renewable energy or biofuel), South America (13%, self-feeding and renewable energy production). ) (Lamptey et al., 2008, Msangi et al., 2010, Tilman et al., 2009). It has previously been found that there is a direct relationship between increased cassava production and the concentration of cyanide released into the environment (Sundaresan et al., 1987; Ibitoye, 2011). This is because higher global temperatures and the hottest years have led to spoilage of crops and reduced the amount of agricultural products, including cassava, reaching the market (Zidenga, 2011; Zidenga et al., 2012).
Recently, cassava plants have been cultivated in the northeastern (Allemann & Dugmore, 2004; Allie et al., 2014) and southwestern regions of the country, which were previously known as cold regions due to changes in weather conditions.1 Thus, favorable growing conditions will lead to increased production. cassava, which will result in an increase in the release of HCN to the environment through volatilization (Allemann & Dugmore, 2004; Lary, 2005; Allie et al., 2014).
ISOLATION OF AN ENDOPHYTIC CYANIDE-RESISTANT FUNGUS CUNNINGHAMELLA
- O BJECTIVES
- M ATERIALS AND M ETHODS ( SUMMARY )
- R ESULTS AND D ISCUSSION
- C. bertholletiae isolation/identification, DNA extraction, phylogenetic tree construction
- Phylogenetic tree analysis
- Fungal degradation of free cyanide, ammonium-nitrogen and nitrogen-nitrate
- S UMMARY
Manihot esculenta (cassava) is considered an essential food source for many poor rural communities in Africa and around the world (Soto-Blanco & Górniak, 2010; Piero et al., 2015). Human health concerns are related to consumption of contaminated tubers, inhalation of fungal microspores which often result in internal organ cancer, pulmonary disease, among others, even when exposure is through skin contact (Peraica & Domijan, 2001; Breitenbach et al., 2002; Klich, 2009; Petraitis et al., 2013). Among this host of pathogenic fungi, Cunninghamella sp., an obscure and opportunistic soil fungus, has the ability to rapidly and fatally infect humans (Lilleskov et al., 2002; Knudsen, 2006; Righi et al., 2008).
Cassava tubers contain cyanide (cyanogenic compounds) which hydrolyzes to hydrogen cyanide which is harmful to human health when consumed in high doses (Mburu et al., 2012). A microscopic observation showed elongated mycelial sporangiophores with irregular, sometimes vertical branches terminated by balloon-shaped vesicles (Álvarez et al., 2011; Guo et al., 2015). Internally transcribed spacers and structural ribosomal DNA sequences of the 5.8S rDNA isolate were amplified using the universal primers ITS1 and ITS4 in order to amplify the 750 bp target region (White et al., 1990). .
In addition, ITS rDNA sequence analysis of isolates is also used during the identification and characterization of fungal species (Lategan et al., 2012).
SCREENING OF FUNGAL (CUNNINGHAMELLA BERTHOLLETIAE) PATHOGENIC
- I NTRODUCTION
- O BJECTIVES
- M ATERIAL AND M ETHODS ( SUMMARY )
- R ESULTS AND D ISCUSSION
- Biochemical identification of microorganisms from cassava-cultivated soil using the VITEK 2 Systems
- S UMMARY
The presence of pathogenic fungi such as Cunninghamella sp. may contribute to the imbalance between the two microbial communities in cassava-grown soils. This part of the research focused on detecting the pathogenic activity of fungi (C. bertholletiae) on some soil microbial communities grown with cassava. Screen the isolate (identified in phase 2: objective 2) for pathogenic activity against several (n = 12, from point 1 above) soil microorganisms (bacteria and fungi) from cassava-grown soil.
Cunninghamella bertholletiae's pathogenic activity against bacteria such as Oligella ureolytica, Acinetobacter sp., Pseudomonas luteola, Sphingomonas paucimobilis, Myroides sp., Achromobacter denitrificans, Achromobacter xylosoxidans, Methylobacterium sp. Instead, there was a kind of symbiosis (Minerdi et al., 2002; Kobayashi & Crouch, 2009), a mutual and beneficial coexistence between a fungus (C. bertholletiae) and the bacteria characterized by mutual growth of both species (Figure) 6-1g) under co-culture conditions (Partida-Martinez & Hertweck, 2005; Partida-Martinez et al., 2007; Kobayashi & Crouch, 2009). However, there was a variation in forms among the microorganisms from rods (Oligella ureolytica, Candida lipolytica, cocci (Acinetobacter family), rods, chains, some singular, (Achromobacte sp.), to rods, small, chains and singular ( Methylobacterium sp. .) and long rods (Rhodotorula sp. and Cryptococcus albidus).
Results revealed numerous bacterial species, namely Oligella ureolytica, Acinetobacter sp., Sphingomonas paucimobilis, Myroides sp., Achromobacter denitrificans, Achromobacter xylosoxidans, Stenotrophomonas maltophilia, Sphingomonas paucimobileus sp., Cethylbacterium sp. tica and fungi such as Cryptococcus albidus, Rhodotorula sp.
RAPID IDENTIFICATION OF CYANIDE-TOLERANT CUNNINGHAMELLA
- I NTRODUCTION
- O BJECTIVES
- M ATERIAL AND M ETHODS (S UMMARY )
- R ESULTS AND D ISCUSSION
- Results
- D ISCUSSION
- Mycotoxins identified from the cyanide resistant Cunninghamella sp
- Biodegradation by-products: outcomes of the mitigation strategy
- S UMMARY
Post-harvest storage of cassava is often shortened due to the production of maceration caused by bacterial and fungal attack (Hocking, 1997; Zidenga et al., 2012). Similarly, and according to Plattner (1995) and Malone et al. 1998), DON detection is readily achieved by HPLC/LC-MS and UV methods. Previous studies showed that biodegradation of fumonisin B1 yielded by-products such as heptadecanone, octadecanamide and octadecenal (Benedetti et al., 2006; Vanhouette et al., 2016).
Furthermore, disturbances and inhibition of blood cells were also reported (Pestka & Smolinski, 2005; Van De Walle et al., 2010), which may ultimately lead to death. According to Duvick et al. 2003), the biodegradation of Fumonisin using Exophiala sp. byproducts such as 2-oxo-12,16-dimethyl-icosanepentol hemiketal and N-acetylated aminopentol backbone (N-acetylAP1). A study by Benedetti et al. 2006) revealed that Fumonisin biodegradation by a combination of Delftia/Comamonas sp.
In general, it has been found that the ability of bacteria to biodegrade toxins such as fumonisin can be achieved by enzymatic biocatalysis (Duvick et al., 2003; Heinl et al., 2009; Vanhoutte, 2016).
OVERALL SUMMARY, CONCLUSIONS AND RECOMMENDATIONS
- O VERALL SUMMARY
- O VERALL CONCLUSION
- R ECOMMENDATIONS : FUTURE STUDIES
Cyanogens such as linamarin contained in produce are released/evaporated during its cultivation, harvesting, processing and cooking. An assessment of the amount of cyanogens, i.e. CN-, released during one of these phases (namely, cultivation) elucidated its contributing role to the overall cyanide load in the environment. As an indicator of plant health when vaporized, gas measurements were made.
In addition, the pathogenicity of the fungus on other soil fungi such as Cryptococcus albidus and Rhodotorula sp. was found to be negligible (Chapter 6). Regarding mitigation or bioremediation strategies with the potential to also facilitate CN- and total nitrogen reduction, Nepenthes mirabilis extracts were successfully evaluated for the specific biodegradation of FB1 and DON by carboxylesterases, β-glucosidase, β-glucoronidase and phosphatidyl inositol phospholipase C. enzymes, which are quantitatively and qualitatively identified as some constituents in the extracts. The novelty of the research was not only in the tolerance and ability of the isolates to biodegrade free cyanide and convert it into NH4+-N and NO3-N and finally into N2 gas, but also in its ability to produce mycotoxins/toxins (FB1, DON). ), including other secondary metabolites that were not of interest in this study.
Finally, an economic evaluation and feasibility of the proposed mycotoxin/CN mitigation method (proposed) on a large scale or in situ/pilot studies are needed to understand the financial implications and to evaluate native plant extracts with the potential to produce extracts with similar properties as observed for Nepenthes mirabilis to ensure the sustainability of the proposed method and to consider alternative plant sources.
BIBLIOGRAPHY
- B IBLIOGRAPHY
Potential for cassava production in the Bathurst region of the Eastern Cape Province of South Africa. Cytochromes P-450 from Cassava (Manihot esculenta Crantz) catalyzing the first steps in the biosynthesis of the cyanogenic glucosides linamarin and lotaustralin-cloning, functional expression in Pichia pastoris and substrate specificity of the isolated recombinant enzymes. Strategic Environmental Assessment, an assessment of the impact of cassava production and processing on the environment and biodiversity.
Aflatoxin and fumonisin contamination of cassava and maize grain products from markets in Tanzania and the Republic of Congo. Evaluation of effects of cassava mill runoff on microbial populations and physicochemical parameters at different soil depths. In-situ enzyme activity in the digested and granulated fraction of juice from four pitcher plant species of the genus Nepenthes.
An Assessment of the Potential for In Situ Bioremediation of Cyanide and Nitrate Contamination at a Central New Mexico Heap Mine.
CHAPTER 10
- APPENDICES
Beans, cotton, sorghum, barley, wheat, corn, cassava, jam, almond, mango, garlic, apple, pineapple, strawberry, pistachio, apricot, peach, carrot, citrus (Citrus sp.), grapes, raisins, figs, milk , Cheese, Date, Corn, Coffee Bean, Onion, Red Pepper.
