Ishmael Amoako-Attah

Cocoa bean quality is strongly influenced by microbial fermentation, which drives flavour development through enzymatic activity. Despite its importance, the specific microorganisms, particularly those producing pectinase, remain poorly characterized. This study aimed to identify and evaluate pectinase-producing microbes from fermenting cocoa mass and assess their impact on fermentation performance. In the first experiment, 9 bacterial and 14 yeast strains were isolated and screened on pectinase screening agar. Three yeast strains (FF1D3, FF2D1, and NA) showed high pectinolytic activity. FF1D3 and FF2D1 were identified as Pichia kudriavzevii, whereas NA showed only a low-confidence closest BLAST match to Candida orthopsilosis and was therefore not advanced as a starter culture candidate. These strains had the highest polygalacturonase activity at 24–48 h and pectin lyase activity at 48–72 h. In the second experiment, inoculating cocoa beans with these strains significantly enhanced fermentation kinetics, with yeast populations reaching log10⁹, indicating enhanced fermentation via accelerated sugar utilization. Brix values (1.97–3.11) and pH reduction (p < 0.01) confirmed active microbial metabolism and effective acidification. Phenolic content varied significantly (p < 0.01), with FF2D1 and combined treatments showing elevated levels due to strain-dependent enzymatic hydrolysis. The combined starter culture showed potential to improve fermentation consistency and accelerate sugar utilization. These findings highlight the potential of targeted microbial inoculation to optimise cocoa fermentation and quality.

Cocoa tree (Theobroma cacao L.) is the source of raw materials for the chocolate industry, which is valued at US$420 billion (ICCO 2023). Protection of the cocoa tree against diseases is crucial fo...

Plants are known to possess antimicrobial properties, as such, their extracts remain potential sources of eco‐friendly antimicrobial products. Extracts from sweet orange have been evaluated as potential antimicrobial sources. However, their activity against pathogens of major agricultural crops such as cocoa is unknown. In this study, the essential oil (EO) of the peel of sweet orange was evaluated against Marasmiellus scandens and Erythricium salmonicolor , the pathogens, respectively, responsible for causing white thread blight and pink disease on cocoa. Minimum Inhibitory Concentration (MIC), IC ₅₀ , IC ₉₀ , and IC ₉₅ against mycelial growth of the pathogens were determined by agar plate tests following 7 days of incubation. Mycelial growths of the two pathogens were completely (100%) inhibited at 10% (w/v) of the EO. The MIC, IC ₅₀ , IC ₉₀ , and IC ₉₅ against M. scandens were 0.1%, 0.25%, 1.23%, and 2.11% while those against E. salmonicolor were 0.01%, 0.13%, 0.75%, and 1.35%, respectively. This study shows that EO of sweet orange peel has antifungal activity against the pathogens. Determining the bioactivity of the individual compounds in the EO and field application of effective formulations in future research has potential for the biological control of these fungal diseases of cocoa.

Thread blight disease (TBD) is a serious emerging threat to global cacao production, causing leaf blight symptoms and necrosis in the canopy of infected trees. Though previously thought to be cause...

Erythricium salmonicolor is the cause of pink disease in cocoa in the humid tropics. The growth of 4 isolates (ES-WR006, ES-WR008, ES-ER009 and ES-ER010) of the fungus on different sources of nutrient (carbohydrate, amino acid and vitamin) and environmental conditions (temperature, pH and light) were evaluated in the laboratory. The pink disease isolates utilised the nutrients to different extent, with the best radial mycelial growth rate achieved with isolate ES-WR008 followed by ES-WR006. None of the isolates produced spores in the laboratory. The isolates utilised polysaccharides as best as disaccharides and monosaccharaides. Among 7 amino acids assayed, aspartic acid was the most promising for vegetative growth. The best radial mycelial growth on vitamins was attained on folic acid and riboflavin. The minimum, optimum and maximum temperatures for growing the fungus were 18 °C, 28 °C and 34 °C respectively. Survival of E. salmonicolor isolates within the temperature range of 18-34 °C is consistent with temperatures for growing cocoa in Ghana. The isolates also grew well within a pH range of 4-8, with the best growth at pH 6. Light quality and duration influenced the vegetative growth of the isolates. Pink disease isolates maintained in 24 hr darkness or 24 hr light performed better than in alternating 12 hr darkness and 12 hr light. There was a significant (p<0.05) repressive effect of the alternating dark and light exposures on vegetative growth of the fungus. The implications of the results for efficient management of the cocoa disease are discussed.

Elucidating the post-harvest quality of marketable kola nuts is essential in developing standards for grading the nuts. This was done in the present study by quantifying the phytochemicals and determining the moulds associated with kola nuts using standard laboratory methods. Mould and phytochemical assessments have both health and safety implications to marketers and consumers. Fresh and cured (3 months) kola nuts of three colour types (red, white, pink) were obtained from three different kola growing regions (Eastern, Ashanti, Ahafo) in Ghana for assessment. There were no significant differences in the amount of phytochemicals in fresh and cured nuts except for moisture (fresh = 56.21 − 59.42%; cured = 53.70–57.99%) and total polyphenol (fresh = 42.6–59.30 mg g-1; cured = 45.51–73.01 mg g-1) contents. Phytochemicals in the nuts after curing were as follows: pH 5.81–5.92, fat 0.49–0.60%, crude fibre 4.62–8.44%, total ash content 2.85–3.01%, alkaloids 0.40–0.99%, saponins 0.29–1.27%, terpenoids 0.30–1.09%, flavonoids 0.76–0.82% and tannins 38.67–45.22 mg g-1. These values are comparable to limits reported in kola nuts consumed in other countries. However, moisture, crude fibre, total polyphenols, alkaloids, saponins and terpenoids contents significantly (p < 0.05) differed across the sampled regions in Ghana. A total of 30 moulds belonging to 14 genera were isolated from the kola nuts. These were Absidia, Aspergillus, Colletotrichum, Fusarium, Fusoma, Geothricum, Gliocladium, Mucor, Neurospora, Penicillium, Rhizoctonia, Rhizopus, Syncephalastrum and Trichoderma. Most Aspergillus, Fusarium and Penicillium species detected are known mycotoxin-producing moulds. The information serves as a useful basis to optimize post-harvest processes of kola nuts to maintain high quality and safety nut for consumption.

Outbreak of anthracnose of cacao (Theobroma cacao L.), covering an estimated total growing area of 248.47 hectares, occurred in parts of Ghana from July to October 2019. Disease samples were collected from the outbreak areas to isolate and identify the pathogen and establish its pathogenicity. Disease symptoms appeared on leaves as dark brown patches with yellow halo margins. Colletotrichum gloeosporioides s.l. was isolated from infected plant tissues and pathogenicity tests confirmed it as the causative agent. The disease was widespread in the Prestea-Huni Valley district of the Western Region, particularly in the Yareyeya community, where a 14.8-hectare farm was seriously affected. Anthracnose has long been known as a sporadic but minor disease of cacao in Ghana. The current shift in status and rapid spread of the disease from infected farms to new farms, though it may or may not be contiguous, cannot be readily explained. Application of copper fungicides, namely Nordox 75 WG (86% cuprous oxide), Champion (77% cupric hydroxide) and Royal Cop 50 WP (77% copper hydroxide) at 75 g, 100 g and 100 g, respectively, each in 15 litres of water, at 2-week intervals for four months, effectively managed the disease.

Theobroma cacao (chocolate tree) is currently under serious threat from thread blight disease (TBD), which has been attributed to the causal agent Marasmiellus scandens in other regions of the world. TBD in Ghana has similar symptomology but variable signs. This study sought to determine whether TBD in Ghana was caused by a single agent and whether Marasmiellus scandens was a significant agent of TBD. Forty-eight isolates were collected from eight geographical locations in Ghana for morphological and molecular characterization. Disease signs occurred as vegetative rhizomorphs or hyphal aggregates, which were classified into five morphotypes: A, abundant thin, black, “horse hair”-type rhizomorphs; B, scattered brown rhizomorphs; C, whitish to brownish-white; D, faint cream or dull white; and E, aggregates of shiny or silky white hyphae. Sequencing and analyses of three loci—the internal transcribed spacer region of the nuclear ribosomal repeat, nuclear large subunit, and mitochondrial small subunit—detected four species, all members of the Marasmiaceae, causing TBD-like disease. These were identified as Marasmius crinis-equi (morphotype A), Marasmius tenuissimus (morphotypes B and C), Marasmiellus palmivorus (morphotype E), and Marasmiellus scandens (morphotype D). Marasmius tenuissimus, the most frequently isolated TBD fungus in this study, is primarily an Asian fungus and not previously associated with diseases of cacao. Marasmiellus palmivorus, the second most frequently isolated fungus, is a pan-tropical pathogen with a broad host range; this is the first report of the fungus causing TBD on cacao. Marasmius crinis-equi also has a broad pan-tropical distribution and host range and causes thread blight on several tropical tree crops. Surprisingly, Marasmiellus scandens, the most frequently cited agent of TBD in cacao, made up only 8% of the isolates.