Heap Fermentations Research Articles

Beneficios de la fermentación de cacao (Theobroma cacao) en la industria alimentaria

This study assesses the impact of different fermentation methods on the organoleptic properties and quality of cocoa beans. Three main techniques were analyzed: fermentation in jute sacks, heap fermentation, and box fermentation. Fermentation in jute sacks, though a traditional method, faces limitations in fermentation efficiency and proper drainage, often resulting in partial and heterogeneous fermentation. On the other hand, heap fermentation is commonly adopted by small producers due to its low cost and ease of implementation; however, it requires meticulous management, including regular turning, to ensure uniform fermentation and quality in the final product. In contrast, box fermentation is identified as the most controllable and effective method, significantly influencing the sensory profile of the bean through specific selection of the type of wood used. Comparative tests indicate a notable improvement in bean quality with this method, making it the preferred choice for producing high-quality chocolate. This analysis underscores the critical importance of selecting an appropriate fermentation method to optimize the sensory characteristics of cocoa and meet the quality expectations in today's chocolate market.

Exploring the impact mechanisms on different mechanized airing approaches during second round heap fermentation of sauce-flavor Baijiu: From physicochemical parameters, microbial diversity to volatile flavor compounds

The airing process of sauce-flavor Baijiu is a critical operation that serves the functions of cooling, homogenizing, and facilitating microbial proliferation and metabolism. Comprehensive analysis of physicochemical parameters, bacterial and fungal community of fermented grains, and volatile flavor compounds of soy-sauce (Jiangxiang) and mellow-sweet (Chuntian) typical base liquors among traditional (CT) and two different mechanized (JXA and JXB) airing operations were investigated. The results indicated that the dynamic variation patterns of moisture content, total titratable acidity, starch content, lactic acid, acetic acid, pH, and dominated microbial composition among CT, JXA, and JXB were similar, while minor bacterial genera with relative abundance including unclassified Micrococcineae, unclassified Rhizobiales, etc, and dominated fungi such as Torulaspora, Hyphopichia, Candida, Pichia, and Penicillium were profoundly influenced by mechanized airing operations, especially by JXB. A total of 100 and 101 volatile flavor compounds were qualitatively and quantitatively detected from soy-sauce (Jiangxiang) and mellow-sweet (Chuntian) typical base liquors. Mechanized airing operations were more consistent with CT for mellow-sweet (Chuntian) typical base liquors, but 2,3-dimethyl-5-ethylpyrazine, 2,3-dimethylpyrazine, tetramethylpyrazine and ethyl benzoate etc. were more abundant in soy-sauce (Jiangxiang) typical base liquors by mechanized airing operations, which were mainly associated with Leuconostoc, Acetoanaerobium, Limnohabitans and Bradyhizobium etc. This study provides a theoretical evidence for understanding the relationships among physicochemical parameters, microbial communities and volatile flavor compounds during second round heap fermentation of sauce-flavor Baijiu, laying a foundation for further elucidating the mechanized brewing mechanisms.

Analysis of microbial community succession and its metabolic characteristics in the first and second rounds of cave-brewed sauce-flavor Baijiu

The natural cave located on the bank of the Chishui River in Guizhou is currently the only base in the country for brewing sauce-flavor Baijiu in the cave. Utilizing the natural cave for brewing not only enriches the microbial source of sauce-flavor Baijiu, but also helps in conserving land resources. This article studied the microbial communities and flavor compounds of fermented grains and the environmental microorganisms during the first and second rounds of heap fermentation in cave-brewed sauce-flavor Baijiu (CBSB). The results indicated that Thermomyces, Torulaspora, and Thermoascus were the dominant fungal genera during heap fermentation, while Virgibacillus, Kroppenstedtia, and Bacillus were the dominant bacteria. Daqu contributed 92.28% of the bacterial community and 73.89% of the fungal community to the fermented grains, while the cave air contributed 11.77% of the fungal community. During the heap fermentation process, a total of 79 volatile metabolites were identified, dominated by esters and alcohols. At the same time, 134 non-volatile metabolites were detected and most amino acids content increased gradually with heap fermentation time, while flavonoids showed the opposite trend. Correlations revealed that Saccharomyces was positively correlated with a number of esters and alcohols, and that Oceanobacillus promoted the synthesis of most flavonoids and organic oxides. The study provides data parameters for the environmental microbiology of the cave and also supports the exploration of the fermentation mechanism of CBSB.

Comparison of Cocoa Bean Quality Produced with Different Starter Cultures and Fermentation Methods

<i>Saccharomyces cerevisiae</i>, <i>Lactobacillus plantarum</i> and <i>Acetobacter tropicalis</i> and <i>Shah</i> (maize-based fermented broth) was used as starter cultures in fermentations and the quality of cocoa bean produced assessed. This was a cross sectional study. Experiments were performed at JPJ Biotechnology Laboratory at IRAD Ekona, Cameroon from March – October, 2020. Fermentations of 10kg were performed in buckets and heaps. These were inoculated with 10^⁶CFU/mL per kg of cocoa bean for Composed Starter (CS) and 100 mL per kg of cocoa for <i>Shah</i>. Samples were collected every day for 5 days. Dried beans from Day 3 onwards of fermentation were assessed using cut-test and Equivalent per cent Fully Brown Score (EB_Score) while the Fermentative Index (FI) was carried out on dried beans of the 5 days. Means were compared using Analysis of Variance and a <i>p </i>-<i> </i>value < 0.05 was considered significant. Good cocoa bean quality (CBQ) with a cut-test of 66% and 62% was respectively obtained with CS and <i>Shah</i> after 3 days in bucket. Natural fermentation attained 62% fully brown beans after 4 days. The CBQ from heap fermentation with CS reached 64% after 4 days while all others remained moderate. Calculated EB_scores were not significantly different except for heap fermentations with values of Day 4 and 5 being higher. By Day 3, CS (FI=1.06) and <i>Shah</i> (FI=1.01) had FI values >1 suggesting that these bucket fermentations could be terminated. In the heap fermentation, good CBQ with CS (FI=1.02) was achieve on Day 4. <i>Shah</i> went on to D5 though the value of D4 (0.96) was not significantly different from that of D5 (1.03). An affordable method for cocoa fermentation was proposed using <i>Shah</i>. Good CBQ was attained faster with use of starter cultures and fermentation time was reduced to 3 days. This is the first study to demonstrate that <i>Shah</i> can be used as a starter culture with comparable results to CS for cocoa fermentation.

Effect of Environmental Microorganisms on Fermentation Microbial Community of Sauce-Flavor baijiu

The compositions of the microbial community in fermented grains of Sauce-flavor baijiu produced in different regions have diverse characteristics; however, the reasons for this remain unclear. The present study investigated the contributions of environmental microorganisms to the microbial community as well as the volatile compounds in the fermented grains of Sauce-flavor baijiu produced in the Beijing region using high-throughput sequencing combined with sourcetracker analysis, and compared the differences of environmental microorganism and their roles in the production process of Sauce-flavor baijiu from different regions.The results showed that the environmental microorganisms in the tools were the main contributors of the bacterial and fungal communities in fermented grains during heap fermentation and at the beginning of pit fermentation. At the end of pit fermentation, pit mud was the main environmental source of bacterial community in fermented grains, while tools and Daqu were the main environmental sources of fungal community in fermented grains.Environmental microorganisms thrived on the functional microorganisms in the fermented grains of Sauce-flavor baijiu produced in the Beijing region and thus shaped the profiles of volatile compounds. Environmental microorganisms of Sauce-flavor baijiu in the Guizhou province and the Beijing region differed significantly, which is partially responsible for the distinctive characteristics in the microbial community structure of Sauce-flavor baijiu-fermented grains from different regions.

Turning over fermented grains elevating heap temperature and driving microbial community succession during the heap fermentation of sauce-flavor baijiu

Turning over fermented grains is widely used during the heap fermentation of sauce-flavor baijiu to increase heap temperature, however, the effect of turning over fermented grains on heap fermentation is still unclear. The present study investigated the changes of microbial community structure and volatile compounds before and after turning over by using high-throughput sequencing combined with gas chromatography-mass spectrometry (GC-MS). Firstly, turning over fermented grains lead to a redistribution of acidity and moisture content in different layers of fermented grains and an increase in heap temperature. Secondly, a total of 41 volatile compounds were identified, among which the concentrations of ethanol, phenylethyl alcohol, acetic acid, and ethyl-9,12-octadecadienoate in fermented grains were elevated after turning over. Next, the changes in fermentation parameters altered or enhanced their driving effects on microbial community succession, resulting in reducing the relative abundance of Pediococcus, Aspergillus, Thermoascus and Thermomyces, while boosting the relative abundance of Lactobacillus and Issatchenkia and making these two members as the predominant genera. The bio-heat generated by microbial community succession contributed to a rapid and continues increase in heap temperature. These results provided a basis for understanding the intrinsic mechanism of the traditional brewing process of sauce-flavor baijiu.

Effects of Fermentation Periods and Drying Methods on Postharvest Quality of Cocoa (Theobroma Cacao) Beans in Ghana

Cocoa (Theobroma cacao) contributes significantly to Ghana’s GDP and has made Ghana a recognized leader in the cocoa industry. However, there are myriad problems associated with Ghana’s cocoa bean quality. One such problems stems from farmers paying less attention to the required postharvest activities (fermentation and drying) which contributes significantly to bean quality losses. This study investigated the effect of the duration of the traditional heap fermentation period and different drying methods: solar biomass hybrid dryer (SBHD) and traditional sun drying method (TSDM) on the bean quality of two cocoa varieties (hybrid cocoa and Amazonia). Quality attributes of cocoa beans such as pH, moisture content, fat content, crude protein, free fatty acids, phenolic contents, colour, and bean size were examined. The statgraphics statistical tool was used to analyse data and the least significant difference (LSD) was used to compare treatment means. Purple beans incidence was observed to be lower in hybrid with a value of 21.90% in the solar biomass hybrid dryer after 5 days of fermentation. Hybrid recorded the highest flavonoid value of 6069.74 mg QE/g DW in the traditional sun drying after 7 days of fermentation. Hybrid as well recorded the highest total phenolic value of 711.44 mg GAE/g DW in the solar biomass hybrid dryer under 5 days of fermentation. Results also indicated that using the solar biomass hybrid dryer resulted in the best moisture content removal and was very efficient compared with the traditional sun drying method in ensuring high-quality beans per international market standards. Cocoa beans dried under SBHD had the overall highest purity and were of better quality compared to those dried directly in the sun. There were no significant differences (p≤0.24) in percentage purity among the cocoa samples studied.

Impact of Seasonal Variation and Processing Methods on the Cassava-Derived Dietary Cyanide Poisoning, Nutritional Status, and Konzo Appearance in South-Kivu, Eastern D.R. Congo

This study aimed at evaluating the impact of seasons on the nutritional status and on dietary cassava-related cyanide exposure in Burhinyi and Idjwi, two areas in the eastern Democratic Republic of the Congo, witnessing similarly high cassava-derived cyanide poisoning but differently affected by konzo and malnutrition. Cyanide content in cassava roots and flour, and urinary thiocyanate levels (uSCN) of 54 subjects (40 from Burhinyi and 14 from Idjwi, aged 28.7 (12.1) years, 63% women) were measured during the rainy season (RS) and dry season (DS), using picrate paper kits A and D1. Local processing methods proved to be efficient in removing cyanogenic compounds in fresh cassava roots during the RS. However, the cyanide content in flour samples significantly increased during DS, with ~50% of samples containing unsafe levels (&gt;10 ppm) of cyanide content. Strikingly, the uSCN (µmol/L), from being comparably high in RS (~172.0), slightly decreased during DS in Burhinyi (~103.2; p = 0,3547), but not in Idjwi (~172; p = 0,1113). Furthermore, serum proteins and albumin levels significantly decreased during the DS, witnessing a worsening of nutritional status, in Burhinyi but not in Idjwi. The consumption of bitter cassava roots (OR = 5.43, p = 0.0144) and skipping heap fermentation (OR = 16.67, p = 0.0021) were independently associated with very high uSCN levels during the DS. Thus, restoring the traditional processing methods, and complying with them in either season should ensure the safe consumption of cassava.

Microbial Community Succession and Its Environment Driving Factors During Initial Fermentation of Maotai-Flavor Baijiu.

The microbial composition and environmental factors can take a great influence on community succession during the solid-state fermentation (SSF) of Maotai-flavor Baijiu. In this paper, high-throughput sequencing was used to reveal the dominant microorganisms and the evolution process of microbial community structure in the initial fermentation of Maotai-flavor Baijiu. The correlation analysis was carried out for the relationship between physicochemical factors and fermented microbes. The results showed that microorganisms were obviously enriched and the diversity of bacteria and fungi showed a downward trend during the heap fermentation process of Maotai-flavor Baijiu. However, the diversity of fungi in the pit fermentation process increased. Generally, Lactobacillus, Pichia, and Saccharomyces were the dominant microorganisms in the initial fermentation of Maotai-flavor Baijiu. According to the redundancy analysis, we found that reducing sugar was the key driving factor for microbial succession in the heap fermentation, while acidity, alcohol, and temperature were the main driving forces in pit fermentation. This study revealed the microbial succession and its related environmental factors in the initial fermentation of Maotai-flavor Baijiu, which will enrich our knowledge of the mechanism of solid-state liquor fermentation.

Effects of initial temperature on microbial community succession rate and volatile flavors during Baijiu fermentation process

The importance of fermentation temperature has been highlighted as it correlates with biodiversity and microbial metabolism for a microbial community. In this study, microbial community succession and volatile flavors during sauce-flavor Baijiu fermentation at different initial temperatures (LT group: 28 ± 2 °C and HT group: 37 ± 2 °C) were investigated using Illumina Miseq sequencing and gas chromatography-mass spectrometry (GC-MS). First, we found that different initial temperatures had a significant effect on fermentation parameters (P < 0.001); specifically, a higher initial temperature increased the accumulation of acetic acid and decreased the production of ethanol. Second, the microbial communities were characterized by decreased α-diversity and increased β-diversity (P < 0.05) during heap fermentation. A higher initial temperature accelerated the increase in Lactobacillus and led to a faster microbial succession rate. Lactobacillus could be used as microbial markers of microbial succession rate in sauce-flavor Baijiu fermentation. Next, we found that acetic acid drove microbial succession under a higher fermentation temperature. Molecular ecological network analysis showed that different fermentation temperatures affected microbial interactions. The higher temperature enhanced microbial interactions of Lactobacillus. In addition, 50 volatile flavors were identified in the fermented grains. High temperature increased the content of total acid and reduced total esters, and Lactobacillus and Saccharomyces were the important microbiota related to different flavor compounds between the two groups. Collectively, altering the initial temperature led to differences in microbial succession rates and volatile flavors in the sauce-flavor Baijiu fermentation process. Therefore, these results are valuable for exploring quality control and management strategies in the spontaneous fermentation process.

Effect of Pichia on shaping the fermentation microbial community of sauce-flavor Baijiu

In spontaneous food fermentation processes, environmental microbiota affects the yield and quality of the fermentation productions. Although the importance of environmental microbiota has been highlighted, the ecological processes that how the environmental microbiota affects the fermentation microbial community are poorly understood. To study the effect of the environmental microbiota on community assembly, the sources of microbiota and the ecological processes of the fermentation were characterized in sauce-flavor Baijiu. Results showed that the process of sauce-flavor Baijiu making could be divided into three phases according to fermentation parameters. Heap fermentation (phase I) was an important period for rapid temperature rise, substrate utilization and production accumulation. The microbial community of heap fermentation was characterized by decrease of diversity and rapid succession of community structure. Virgibacillus, Kroppenstedtia, Bacillus and Oceanobacillus were predominant in the initial heap fermentation, while Lactobacillus was predominant during the later stage. Pichia was the predominant fungal genus during the whole fermentation process. Then, SourceTracker results showed that Daqu provided 95.6% of the bacterial community and 28.10% of the fungal community to heap fermentation, whereas the environments (indoor ground and tools) provided 71.9% of the fungal communities (mainly Pichia) to heap fermentation. Next, the results revealed that the temperature, ethanol and microbial interaction of Pichia synergistically drove the dynamic of the microbial community during the heap fermentation process. Pichia was proved to be the heat-resistant fungi and strong competitor based on growth in different temperature and competition assays in vitro. Finally, the quick succession of heap fermentation microbiota increased the enrichment of volatile flavors such as acids and esters. Our comprehensive methods shows that Pichia, which mainly comes from the environment, can construct the microbial community of Baijiu fermentation, and highlights the importance of environmental microbiota in attempts to control and promote the formation of Baijiu fermentation microbial community. This systematic study of environmental microbiota is valuable for quality control and management during spontaneous fermentation.

Development and Characterization of a Pilot-Scale Model Cocoa Fermentation System Suitable for Studying the Impact of Fermentation on Putative Bioactive Compounds and Bioactivity of Cocoa.

Cocoa is a concentrated source of dietary flavanols—putative bioactive compounds associated with health benefits. It is known that fermentation and roasting reduce levels of native flavonoids in cocoa, and it is generally thought that this loss translates to reduced bioactivity. However, the mechanisms of these losses are poorly understood, and little data exist to support this paradigm that flavonoid loss results in reduced health benefits. To further facilitate large-scale studies of the impact of fermentation on cocoa flavanols, a controlled laboratory fermentation model system was increased in scale to a large (pilot) scale system. Raw cocoa beans (15 kg) were fermented in 16 L of a simulated pulp media in duplicate for 168 h. The temperature of the fermentation was increased from 25–55 °C at a rate of 5 °C/24 h. As expected, total polyphenols and flavanol levels decreased as fermentation progressed (a loss of 18.3% total polyphenols and 14.4% loss of total flavanols during fermentation) but some increases were observed in the final timepoints (120–168 h). Fermentation substrates, metabolites and putative cocoa bioactive compounds were monitored and found to follow typical trends for on-farm cocoa heap fermentations. For example, sucrose levels in pulp declined from >40 mg/mL to undetectable at 96 h. This model system provides a controlled environment for further investigation into the potential for optimizing fermentation parameters to enhance the flavanol composition and the potential health benefits of the resultant cocoa beans.

Dynamics and Biodiversity of Bacterial and Yeast Communities during Fermentation of Cocoa Beans.

Forastero hybrid cocoa bean fermentations have been carried out in a box (B) and in a heap (H), with or without the inoculation of Saccharomyces cerevisiae and Torulaspora delbrueckii as starter cultures. The bacteria, yeasts, and microbial metabolites (volatile and nonvolatile organic compounds) were monitored during fermentation to assess the connection between microbiota and the release of metabolites during this process. The presence of starter cultures was detected, by means of culture-dependent analysis, during the first 2 days of both fermentations. However, no statistical difference was observed in any of the physicochemical or microbiological analyses. Plate counts revealed the dominance of yeasts at the beginning of both fermentations, and these were followed by acetic acid bacteria (AAB) and lactic acid bacteria (LAB). Hanseniaspora opuntiae, S. cerevisiae, Pichia pijperi, Acetobacter pasteurianus, and Lactobacillus fermentum were the most abundant operational taxonomic units (OTUs) during both fermentation processes (B and H), although different relative abundances were observed. Only the diversity of the fungal species indicated a higher level of complexity in the B fermentations than in the H fermentations (P < 0.05), as well as a statistically significant difference between the initially inoculated starter cultures (P < 0.01). However, the microbial metabolite analysis indicated different distributions of the volatile and nonvolatile compounds between the two procedures, that is, B and H (P < 0.05), rather than between the inoculated and noninoculated fermentations. The box fermentations showed faster carbohydrate metabolism and greater production of organic acid compounds, which boosted the formation of alcohols and esters, than did the heap fermentations. Overall, the microbial dynamics and associations between the bacteria, yeasts, and metabolites were found to depend on the type of fermentation.IMPORTANCE In spite of the limited effectiveness of the considered inoculated starter strains, this study provides new information on the microbial development of box and heap cocoa fermentations, under inoculated and noninoculated conditions, as we coupled yeast/bacterial amplicon-based sequencing data with microbial metabolite detection. The information so far available suggests that microbial communities have played an important role in the evolution of aroma compounds. Understanding the pathways that microorganisms follow during the formation of aromas could be used to improve the fermentation processes and to enhance chocolate quality.

Effectiveness of Traditional Processing Techniques in Reducing Cyanide Levels in Selected Cassava Varieties in Zombo District, Uganda

The root tubers of cassava (Manihot esculenta Crantz) contain varying amounts of cyanogenic glucosides which liberate toxic hydrogen cyanide with the resultant effect of poisoning especially the highly cyanogenic cultivars. These include some of the local and improved cassava varieties grown in Zombo district, Uganda among others. Therefore, this study explored the effectiveness of some traditional processing techniques used singly and in combination to reduce cyanide levels in highly toxic root tubers of selected local (Nyar-anderiano, Nyar-papoga, Nyar-udota, Nyar-pamitu, Bisimwenge, Nyar-matia) and improved (NASE 3, NASE 9, NASE 14, NASE 19, TME 14 and TME 204) cassava varieties grown in Zombo District, Uganda. The processed and the fresh cassava tubers were analysed for Hydrogen cyanide (HCN) by the standard titration method. The results indicated that heap fermentation followed by sun-drying reduced the cyanide levels in all the selected improved varieties to WHO safe levels for consumption (below 10mg/kg) in the dried chips. Mixed processing methods combining soaking, fermentation and sun-drying reduced the cyanide concentrations in the local varieties (Nyar-udota, Nyar-anderiano) and improved variety (NASE 19) to World Health Organisation (WHO) safe levels. None of the processing techniques used singly reduced the HCN levels in the root tubers of the selected cassava varieties to safe levels. Hence mixed strategies combining several traditional cassava processing techniques should be adopted to detoxify the selected cassava varieties of cyanogens. The local cassava varieties (Bisimwenge, Nya-matia, Nya-pamitu, Nya-papoga) would require modifications of the combined traditional processing techniques or other more complex processes to detoxify them of HCN before human consumption.

The environmental and intrinsic yeast diversity of Cuban cocoa bean heap fermentations

The environmental yeast diversity of spontaneous cocoa bean fermentations in east Cuba was investigated. Seven fermentations, 25 equipment- and handling-related samples, and 115 environmental samples, such as flowers, leaf and cocoa pod surfaces, as well as drosophilid insects, were analysed. The basic fermentation parameters temperature and pH were recorded during five fermentations for at least six days. A total of 435 yeast isolates were identified by a combination of PCR-fingerprinting of genomic DNA with the M13 primer and sequence analysis of DNA from representative isolates, using the internal transcribed spacer region, the D1/D2 region of the large subunit rRNA gene, and an actin gene-encoding fragment, as required. Among 65 yeast species detected, Pichia manshurica and Hanseniaspora opuntiae were the most frequently isolated species, obtained from five and four fermentations, followed in frequency by Pichia kudriavzevii from two fermentations. Saccharomyces cerevisiae was isolated only occasionally. Cocoa fermentation yeast species were also present on processing equipment. The repeated isolation of a preliminarily as Yamadazyma sp. classified species, a group of strains similar to Saccharomycopsis crataegensis from fermentations and equipment, and the isolation of fifteen other potentially novel yeast species in low numbers provides material for further studies. Environmental samples showed higher yeast diversity compared to the fermentations, included the most frequent fermentation species, whereas the most frequently isolated environmental species were Candida carpophila, Candida conglobata, and Candida quercitrusa. Potential selective advantages of the most frequently isolated species were only partly explained by the physiological traits tested. For instance, tolerance to higher ethanol concentrations was more frequent in strains of Pichia spp. and S. cerevisiae compared to Hanseniaspora spp.; the ability to also assimilate ethanol might have conferred a selective advantage to Pichia spp. In contrast, high glucose tolerance was common among strains of Hanseniaspora spp., Torulaspora delbrueckii, and Candida tropicalis, among which only Hanseniaspora spp. were frequently isolated.

Assessment of the contribution of cocoa-derived strains of Acetobacter ghanensis and Acetobacter senegalensis to the cocoa bean fermentation process through a genomic approach

Acetobacter ghanensis LMG 23848T and Acetobacter senegalensis 108B are acetic acid bacteria that originate from a spontaneous cocoa bean heap fermentation process and that have been characterised as strains with interesting functionalities through metabolic and kinetic studies. As there is currently little genetic information available for these species, whole-genome sequencing of A. ghanensis LMG 23848T and A. senegalensis 108B and subsequent data analysis was performed. This approach not only revealed characteristics such as the metabolic potential and genomic architecture, but also allowed to indicate the genetic adaptations related to the cocoa bean fermentation process. Indeed, evidence was found that both species possessed the genetic ability to be involved in citrate assimilation and displayed adaptations in their respiratory chain that might improve their competitiveness during the cocoa bean fermentation process. In contrast, other properties such as the dependence on glycerol or mannitol and lactate as energy sources or a less efficient acid stress response may explain their low competitiveness. The presence of a gene coding for a proton-translocating transhydrogenase in A. ghanensis LMG 23848T and the genes involved in two aromatic compound degradation pathways in A. senegalensis 108B indicate that these strains have an extended functionality compared to Acetobacter species isolated from other ecosystems.

Molecular identification and physiological characterization of yeasts, lactic acid bacteria and acetic acid bacteria isolated from heap and box cocoa bean fermentations in West Africa

Yeast, lactic acid bacteria (LAB) and acetic acid bacteria (AAB) populations, isolated from cocoa bean heap and box fermentations in West Africa, have been investigated. The fermentation dynamics were determined by viable counts, and 106 yeasts, 105 LAB and 82 AAB isolates were identified by means of rep-PCR grouping and sequencing of the rRNA genes. During the box fermentations, the most abundant species were Saccharomyces cerevisiae, Candida ethanolica, Lactobacillus fermentum, Lactobacillus plantarum, Acetobacter pasteurianus and Acetobacter syzygii, while S. cerevisiae, Schizosaccharomyces pombe, Hanseniaspora guilliermondii, Pichia manshurica, C. ethanolica, Hanseniaspora uvarum, Lb. fermentum, Lb. plantarum, A. pasteurianus and Acetobacter lovaniensis were identified in the heap fermentations. Furthermore, the most abundant species were molecularly characterized by analyzing the rep-PCR profiles. Strains grouped according to the type of fermentations and their progression during the transformation process were also highlighted. The yeast, LAB and AAB isolates were physiologically characterized to determine their ability to grow at different temperatures, as well as at different pH, and ethanol concentrations, tolerance to osmotic stress, and lactic acid and acetic acid inhibition. Temperatures of 45°C, a pH of 2.5 to 3.5, 12% (v/v) ethanol and high concentrations of lactic and acetic acid have a significant influence on the growth of yeasts, LAB and AAB. Finally, the yeasts were screened for enzymatic activity, and the S. cerevisiae, H. guilliermondii, H. uvarum and C. ethanolica species were shown to possess several enzymes that may impact the quality of the final product.

Impact of Heap Fermentation of Cocoa on Microbial Dynamics and Soil Physicochemical Parameters

Impact of Heap Fermentation of Cocoa on Microbial Dynamics and Soil Physicochemical Parameters

Biochemical and functional properties of lactic acid bacteria isolated from Ivorian cocoa fermenting beans

Objective: Fermentation is an important step in the post-harvest processing of cocoa beans. The quality of beans and chocolate depends strongly on the type and characteristics of microbial strains involved in the fermentation. This study investigates some functional properties of lactic acid bacteria (LAB), involved in Côte d’Ivoire cocoa fermentation. Methodology and results: Bacterial growth was monitored during spontaneous heap fermentation using plate count and decimal dilution methods. LAB was present throughout the fermentative process with a load comprised between 6.0 log (UFC/g of bean) at the beginning to 6.60 log (UFC/g of bean) at the end. The maximum load of LAB corresponding to 7.22 log (UFC/g of bean) was reached after 24 h of fermentation in the condition of 42 °C of temperature and pH round 3.55. Among the 150 strains isolated, 99 were lactobacilli and 51 lactococci. Almost all these LAB showed ability to ferment glucose, fructose and sucrose with an important acidification capacity while only 8 strains belonging to lactococci proved to be able to assimilate citrate. Moreover, a weak proportion (7.33 %) of LAB strains isolated was heterofermentative type. These heterofermentative LAB strains were particularly characterized by a great fermentative capacity especially with glucose and sucrose with a gas production up to 5 mL. Conclusion and application of results: The citrate metabolism and the strong fermentative capacity of certain LAB strains, indicate interesting technological traits potentially useful for their utilization as starters in cocoa fermentation.Keywords: lactic acid bacteria; fermentative power; cacao fermentation; acidification; citrate metabolism.

Biochemical and functional properties of lactic acid bacteria isolated from Ivorian cocoa fermenting beans

Objective : Fermentation is an important step in the post-harvest processing of cocoa beans. The quality of beans and chocolate depends strongly on the type and characteristics of microbial strains involved in the fermentation. This study investigates some functional properties of lactic acid bacteria (LAB), involved in Cote d’Ivoire cocoa fermentation. Methodology and results : Bacterial growth was monitored during spontaneous heap fermentation using plate count and decimal dilution methods. LAB was present throughout the fermentative process with a load comprised between 6.0 log (UFC/g of bean) at the beginning to 6.60 log (UFC/g of bean) at the end. The maximum load of LAB corresponding to 7.22 log (UFC/g of bean) was reached after 24 h of fermentation in the condition of 42 °C of temperature and pH round 3.55. Among the 150 strains isolated, 99 were lactobacilli and 51 lactococci. Almost all these LAB showed ability to ferment glucose, fructose and sucrose with an important acidification capacity while only 8 strains belonging to lactococci proved to be able to assimilate citrate. Moreover, a weak proportion (7.33 %) of LAB strains isolated was heterofermentative type. These heterofermentative LAB strains were particularly characterized by a great fermentative capacity especially with glucose and sucrose with a gas production up to 5 mL. Conclusion and application of results : The citrate metabolism and the strong fermentative capacity of certain LAB strains, indicate interesting technological traits potentially useful for their utilization as starters in cocoa fermentation. Keywords : lactic acid bacteria; fermentative power; cacao fermentation; acidification; citrate metabolism.