Unravelling the contribution of lactic acid bacteria and acetic acid bacteria to cocoa fermentation using inoculated organisms

Exploring the Impact of Fermentation Time and Climate on Quality of Cocoa Bean-Derived Chocolate: Sensorial Profile and Volatilome Analysis

The market for fine-flavor cocoa provides significant benefits to farmers. However, identifying the sensory qualities of chocolate under specific environmental conditions and measuring how its chemical compounds may be affected by climate differences and postharvesting practices remain a challenge. This study investigates how fermentation time and agroclimatic conditions in Colombia's fine cocoa-producing region of Arauca influence the sensory profile and volatile compound composition (volatilome) of chocolate derived from cocoa beans. Sensory evaluation was conducted on chocolates fermented for 48, 72, 96, and 120 h, revealing that fermentation time critically affects the development of fine-flavor attributes, particularly fruitiness and nuttiness. The optimal fermentation period to enhance these attributes was identified at 96 h, a duration consistently associated with peak fruitiness under all studied climatic conditions. Analysis of 44 volatile compounds identified several key aroma markers, such as acetoin, 1-methoxy-2-propyl acetate, and various pyrazines, which correlate with desirable sensory attributes. These compounds exhibited varying amounts depending on fermentation time and specific agroclimatic conditions, with a 96 h fermentation yielding chocolates with a higher quantity of volatile compounds associated with preferred attributes. Our findings highlight the complex interaction between fermentation processes and agroclimatic factors in determining cocoa quality, providing new insights into optimizing the flavor profiles of chocolate.

Fermentation of coffee fruit with sequential inoculation of Lactiplantibacillus plantarum and Saccharomyces cerevisiae: effect on sensory attributes and chemical composition of the beans

This study has innovative aspects related to the use of sequential inoculation technique in the coffee bean fermentation process: the inoculation of Lactiplantibacillus plantarum followed by Saccharomyces cerevisiae, in the fermentation of coffee fruit for the production of specialty natural coffees. The objective was to evaluate the effect of this technique and of the total fermentation time on the sensory attributes of the coffee beverage and on the organic acid profile, bioactive compounds, and fatty acid profile of the beans. The fermentation of coffee fruit with sequential inoculation resulted in greater acidity of the beverage and contributed to increases of up to 2 points in coffee fermented. The total fermentation time was directly related to the organic acid content, and the longer the total fermentation time was, the greater the organic acid content. The fatty acid content and bioactive compound content showed little variation among treatments.

Soybean fermentation: Microbial ecology and starter culture technology

Fermented soybean products, including Soya sauce, Tempeh, Miso, and Natto have been consumed for decades, mainly in Asian countries. Beans are processed using either solid-state fermentation, submerged fermentation, or a sequential of both methods. Traditional ways are still used to conduct the fermentation processes, which, depending on the fermented products, might take a few days or even years to complete. Diverse microorganisms were detected during fermentation in various processes with Bacillus species or filamentous fungi being the two main dominant functional groups. Microbial activities were essential to increase the bean's digestibility, nutritional value, and sensory quality, as well as lower its antinutritive factors. The scientific understanding of fermentation microbial communities, their enzymes, and their metabolic activities, however, still requires further development. The use of a starter culture is crucial, to control the fermentation process and ensure product consistency. A broad understanding of the spontaneous fermentation ecology, biochemistry, and the current starter culture technology is essential to facilitate further improvement and meet the needs of the current extending and sustainable economy. This review covers what is currently known about these aspects and reveals the limited available information, along with the possible directions for future starter culture design in soybean fermentation.

Investigating luxS gene expression in lactobacilli along lab-scale cocoa fermentations

Previous metagenomic analyses have suggested that lactobacilli present potential for Quorum Sensing (QS) in cocoa fermentation, and in the present research, laboratory scale fermentations were carried out to monitor the expression of luxS, a universal marker of QS. For that, 96 h-fermentations were studied, as follows: F0 (non inoculated control), F1 (inoculated with yeasts, lactic acid bacteria, and acetic acid bacteria), F2 (inoculated with yeasts and acetic acid bacteria), F3 (inoculated with yeasts only). The parameters evaluated were: plate counting, quantification of key enzymes and analysis of volatile organic compounds associated with key sensory descriptors, using headspace gas chromatography-mass spectrometry (GC-MS). Furthermore, QS was estimated by the quantification of the expression of luxS genes by Reverse Transcriptase Real-Time PCR. The results demonstrated that microbial succession occurred in pilot scale fermentations, but no statistical differences for microbial enumeration and α-diversity index were observed among experiments and control. Moreover, it was not possible to make conclusive correlations of enzymatic profile and fermenting microbiota, likely due to the intrinsic activity of plant hydrolases. Regarding to the expression of luxS genes, in Lactiplantibacillus plantarum they were active along the fermentation, but for Limosilactobacillus fermentum, luxS was expressed only at early and middle phases. Correlation analysis of luxS expression and production of volatile metabolites evidenced a possible negative association of Lp. Plantarum with fermentation quality. In conclusion, these data corroborate former shotgun metagenomic analysis by demonstrating the expression of luxS by lactobacilli in pilot scale cocoa fermentation and evidence Lp. Plantarum is the main lactic acid bacteria related to its expression.

Electromagnetic fields effects on microbial growth in cocoa fermentation: A controlled experimental approach using established growth models

Understanding the effects of electromagnetic fields is crucial in the fermentation of cocoa beans, since through precise control of fermentation conditions the sensory and nutritional properties of cocoa beans could be improved. This study aimed to evaluate the effect of oscillating magnetic fields (OMF) on the kinetic growth of the core microbial communities of the Collections Castro Naranjal (CCN 51) cocoa bean. The data was obtained by three different models: Gompertz, Baranyi, and Logistic. The cocoa beans were subjected to different OMF strengths ranging from 0 mT to 80 mT for 1 h using the Helmholtz coil electromagnetic device. The viable microbial populations of lactic acid bacteria (LAB), acetic acid bacteria (AAB), and yeast (Y) were quantified using the colony-forming unit (CFU) counting method. The logistic model appropriately described the growth of LAB and Y under magnetic field exposure. Whereas the Baranyi model was suitable for describing AAB growth. The microbial populations in cocoa beans exposed to magnetic fields showed lower (maximum specific growth rate (μmax), values than untreated controls, with AAB exhibiting the highest average growth rate value at 5 mT and Y having the lowest average maximum growth rate value at 80 mT. The lower maximum specific growth rates and longer lag phases when exposed to magnetic fields compared to controls demonstrate the influence of magnetic fields on microbial growth kinetics.

Natural fermentation with delayed inoculation of the yeast Torulaspora delbrueckii: Impact on the chemical composition and sensory profile of natural coffee

All coffee production stages occur in a microbiome, which is generally composed of bacteria, yeasts, and filamentous fungi. The use of starter cultures in post-harvest processing stages is an interesting alternative, since they promote faster removal of mucilage and incorporation of compounds that improve sensory quality, which can result in diverse sensory attributes for the beverage. This study was therefore developed with the objective of evaluating the effect of the following processing procedures on the chemical and sensory characteristics of the coffee beverage: first, fermentation of coffee fruit of the yellow Catucaí variety of Coffea arabica with indigenous microorganisms, followed by inoculation of the starter culture Torulaspora delbrueckii CCMA 0684 during the drying stage. The fruit was divided into two lots, which were differentiated by a natural fermentation process before drying began. The starter culture was inoculated on the coffee at different times during the drying process: at 0 h, 24 h, 48 h, or 72 h after drying began. The sensory attributes, the volatile compound composition of the roasted beans, the organic acid profile, the bioactive compounds, and the fatty acid profile of the green coffee beans were analyzed. The fatty acid and bioactive compound content showed little variation among treatments. Analysis of volatile compounds and organic acids and evaluation of sensory attributes made it possible to distinguish the two treatments. We conclude that natural fermentation of coffee fruit improve the chemical and sensory quality of the coffee beverage. The effect of natural fermentation may be before inoculation of the starter cultures or even during drying.

An overview of fermentation in the food industry - looking back from a new perspective

Fermentation is thought to be born in the Fertile Crescent, and since then, almost every culture has integrated fermented foods into their dietary habits. Originally used to preserve foods, fermentation is now applied to improve their physicochemical, sensory, nutritional, and safety attributes. Fermented dairy, alcoholic beverages like wine and beer, fermented vegetables, fruits, and meats are all highly valuable due to their increased storage stability, reduced risk of food poisoning, and enhanced flavor. Over the years, scientific research has associated the consumption of fermented products with improved health status. The fermentation process helps to break down compounds into more easily digestible forms. It also helps to reduce the amount of toxins and pathogens in food. Additionally, fermented foods contain probiotics, which are beneficial bacteria that help the body to digest food and absorb nutrients. In today's world, non-communicable diseases such as cardiovascular disease, type 2 diabetes, cancer, and allergies have increased. In this regard, scientific investigations have demonstrated that shifting to a diet that contains fermented foods can reduce the risk of non-communicable diseases. Moreover, in the last decade, there has been a growing interest in fermentation technology to valorize food waste into valuable by-products. Fermentation of various food wastes has resulted in the successful production of valuable by-products, including enzymes, pigments, and biofuels.

A chemically-defined growth medium to support Lactobacillus-Acetobacter sp. community analysis

Lactobacilli and Acetobacter sp. are commercially important bacteria that often form communities in natural fermentations, including food preparations, spoilage, and in the digestive tract of the fruit fly Drosophila melanogaster. Communities of these bacteria are widespread and prolific, despite numerous strain-specific auxotrophies, suggesting they have evolved nutrient interdependencies that regulate their growth. The use of a chemically-defined medium (CDM) supporting the growth of both groups of bacteria would facilitate the identification of the molecular mechanisms for the metabolic interactions between them. While numerous CDMs have been developed that support specific strains of lactobacilli or Acetobacter, there has not been a medium formulated to support both genera. We developed such a medium, based on a previous CDM designed for growth of lactobacilli, by modifying the nutrient abundances to improve growth yield. We further simplified the medium by substituting casamino acids in place of individual amino acids and the standard Wolfe's vitamins and mineral stocks in place of individual vitamins and minerals, resulting in a reduction from 40 to 8 stock solutions. These stock solutions can be used to prepare several CDM formulations that support robust growth of numerous lactobacilli and Acetobacters. Here, we provide the composition and several examples of its use, which is important for tractability in dissecting the genetic and metabolic basis of natural bacterial species interactions.

Biodiversity and biotechnological properties of lactic acid bacteria isolated from traditional Moroccan sourdoughs

The present study aimed at characterizing lactic acid bacteria (LAB) strains isolated from traditional sourdoughs collected in different regions of Morocco. Isolated strains were firstly identified using Gram staining and catalase reaction test. Presumptive LAB strains were then checked for various phenotypical properties including growth at 45 °C, resistance to NaCl, enzyme production, acidification capacity, diacetyl and exopolysaccharide (EPS) production, and antifungal activity. Finally, selected LAB strains were identified using 16S rDNA sequencing. Results showed that 32.1% of the isolates were thermophilic (45 °C) and 83.9% were resistant to NaCl (6.5%). Moreover, 51.7 and 37.5% were able to produce diacetyl and EPS, respectively. Regarding enzyme production, 55.3 and 7.1% of the isolates showed lipolytic and proteolytic activities, respectively. Low pH values (3.37-3.76) were obtained after 24 h of incubation of LAB strains in de Man, Rogosa and Sharpe (MRS) broth. Antifungal activity test against Aspergillus flavus, Aspergillus niger and Penicillium spp. showed an inhibition rate up to 50%. Bacterial DNA sequencing showed that LAB isolates belong to seven species, chiefly Levilactobacillus brevis, Lentilactobacillus parabuchneri, Lactiplantibacillus plantarum, Pediococcus pentosaceus, Enterococcus hirae, Bifidobacterium pseudocatenulatum, and Companilactobacillus paralimentarius. These findings, for the first time in Moroccan sourdoughs, indicate that the isolated LAB strains have good multifunctional properties and could be suitable as good starters for sourdough bread production under controlled conditions.

Yeast strains do have an impact on the production of cured cocoa beans, as assessed with Costa Rican Trinitario cocoa fermentation processes and chocolates thereof

The microbiological and metabolic outcomes of good cocoa fermentation practices can be standardized and influenced through the addition of starter culture mixtures composed of yeast and bacterial strains. The present study performed two spontaneous and 10 starter culture-initiated (SCI) cocoa fermentation processes (CFPs) in Costa Rica with local Trinitario cocoa. The yeast strains Saccharomyces cerevisiae IMDO 050523, Hanseniaspora opuntiae IMDO 020003, and Pichia kudriavzevii IMDO 060005 were used to compose starter culture mixtures in combination with the lactic acid bacterium strain Limosilactobacillus fermentum IMDO 0611222 and the acetic acid bacterium strain Acetobacter pasteurianus IMDO 0506386. The microbial community and metabolite dynamics of the cocoa pulp-bean mass fermentation, the metabolite dynamics of the drying cocoa beans, and the volatile organic compound (VOC) profiles of the chocolate production were assessed. An amplicon sequence variant approach based on full-length 16S rRNA gene sequencing instead of targeting the V4 region led to a highly accurate monitoring of the starter culture strains added, in particular the Liml. fermentum IMDO 0611222 strain. The latter strain always prevailed over the background lactic acid bacteria. A similar approach, based on the internal transcribed spacer (ITS1) region of the fungal rRNA transcribed unit, was used for yeast strain monitoring. The SCI CFPs evolved faster when compared to the spontaneous ones. Moreover, the yeast strains applied did have an impact. The presence of S. cerevisiae IMDO 050523 was necessary for successful fermentation of the cocoa pulp-bean mass, which was characterized by the production of higher alcohols and esters. In contrast, the inoculation of H. opuntiae IMDO 020003 as the sole yeast strain led to underfermentation and a poor VOC profile, mainly due to its low competitiveness. The P. kudriavzevii IMDO 060005 strain tested in the present study did not contribute to a richer VOC profile. Although differences in VOCs could be revealed in the cocoa liquors, no significant effect on the final chocolates could be obtained, mainly due to a great impact of cocoa liquor processing during chocolate-making. Hence, optimization of the starter culture mixture and cocoa liquor processing seem to be of pivotal importance.

Flavor Precursors and Volatile Compounds Improvement of Unfermented Cocoa Beans by Hydrolysis Using Bromelain

Cocoa fermentation is an essential process that produces flavor precursors. However, many small farmers in Indonesia directly dry their cocoa beans without fermentation due to low yield and long fermentation time, resulting in fewer flavor precursors and cocoa flavor. Therefore, this study aimed to enhance the flavor precursors, particularly free amino acids and volatile compounds, of unfermented cocoa beans by hydrolysis, using bromelain. Unfermented cocoa beans were previously hydrolyzed with bromelain at concentrations of 3.5, 7, and 10.5 U/mL for 4, 6, and 8 h, respectively. An analysis of enzyme activity, degree of hydrolysis, free amino acids, reducing sugar, polyphenols, and volatile compounds was then conducted using unfermented and fermented cocoa beans as negative and positive controls, respectively. The results showed that the highest degree of hydrolysis was 42.95% at 10.5 U/mL for 6 h, although it was not significantly different from the hydrolysis at 3.5 U/mL for 8 h. This indicates a higher reducing sugar and lower polyphenols content than unfermented cocoa beans. There was also an increase in free amino acids, especially hydrophobic amino acids, such as phenylalanine, valine, leucine, alanine, and tyrosine, and desirable volatile compounds, such as pyrazines. Therefore, this suggests that hydrolysis with bromelain increased the flavor precursors and cocoa-bean flavors.

Coenzyme self-sufficiency system-recent advances in microbial production of high-value chemical phenyllactic acid

Phenyllactic acid (PLA), a natural antimicrobial substance, has many potential applications in the food, animal feed, pharmaceutical and cosmetic industries. However, its production is limited by the complex reaction steps involved in its chemical synthesis. Through advances in metabolic engineering and synthetic biology strategies, enzymatic or whole-cell catalysis was developed as an alternative method for PLA production. Herein, we review recent developments in metabolic engineering and synthetic biology strategies that promote the microbial production of high-value PLA. Specially, the advantages and disadvantages of the using of the three kinds of substrates, which includes phenylpyruvate, phenylalanine and glucose as starting materials by natural or engineered microbes is summarized. Notably, the bio-conversion of PLA often requires the consumption of expensive coenzyme NADH. To overcome the issues of NADH regeneration, efficiently internal cofactor regeneration systems constructed by co-expressing different enzyme combinations composed of lactate dehydrogenase with others for enhancing the PLA production, as well as their possible improvements, are discussed. In particular, the construction of fusion proteins with different linkers can achieve higher PLA yield and more efficient cofactor regeneration than that of multi-enzyme co-expression. Overall, this review provides a comprehensive overview of PLA biosynthesis pathways and strategies for increasing PLA yield through biotechnology, providing future directions for the large-scale commercial production of PLA and the expansion of downstream applications.

Phylogenomics of a Saccharomyces cerevisiae cocoa strain reveals adaptation to a West African fermented food population

Various yeast strains have been proposed as candidate starter cultures for cocoa fermentation, especially strains of Saccharomyces cerevisiae. In the current study, the genome of the cocoa strain S. cerevisiae IMDO 050523 was unraveled based on a combination of long- and short-read sequencing. It consisted of 16 nuclear chromosomes and a mitochondrial chromosome, which were organized in 20 contigs, with only two small gaps. A phylogenomic analysis of this genome together with another 105 S cerevisiae genomes, among which 20 from cocoa strains showed a geographical distribution of the latter, including S. cerevisiae IMDO 050523. Its genome clustered together with that of a West African fermented food population, indicating a wider adaptation to West African food niches than cocoa. Furthermore, S. cerevisiae IMDO 050523 contained genetic signatures involved in sucrose hydrolysis, pectin degradation, osmotolerance, and conserved amino acid changes in key ester-producing enzymes that could point toward specific niche adaptations.

Adaptive Laboratory Evolution of Yeasts for Aroma Compound Production

Aroma compounds are important in the food and beverage industry, as they contribute to the quality of fermented products. Yeasts produce several aroma compounds during fermentation. In recent decades, production of many aroma compounds by yeasts obtained through adaptive laboratory evolution has become prevalent, due to consumer demand for yeast strains in the industry. This review presents general aspects of yeast, aroma production and adaptive laboratory evolution and focuses on the recent advances of yeast strains obtained by adaptive laboratory evolution to enhance the production of aroma compounds.

Microbial Diversity and Contribution to the Formation of Volatile Compounds during Fine-Flavor Cacao Bean Fermentation

Cacao demand is continuously increasing, and variations in cacao prices have been associated with the aroma of fermented cacao beans. However, the role of microorganisms in the formation of volatile-aroma compounds during fermentation remains unclear. Microbial diversity in Nacional × Trinitario cacao was characterized during spontaneous fermentation by using culture-based methods and next-generation sequencing (NGS) of DNA amplicons. Cacao beans that were spontaneously fermented for 0, 24, 48, 72 and 96 h were UV-sterilized prior to the inoculation of the microbial isolates obtained by the culture-based methods. The volatile formation in inoculated cacao beans was evaluated by GC-MS. The species isolated during fermentation included yeast, such as Saccharomyces cerevisiae and Candida metapsilosis; lactic acid bacteria (LAB), such as Limosilactobacillus fermentum and Liquorilactobacillus nagelii; acetic acid bacteria (AAB), such as Acetobacter pasteurianus, Acetobacter ghanensis and Acetobacter syzygii, as well as other species, such as Bacillus subtilis and Bacillus amyloliquefaciens. Additionally, NGS revealed an abundance of environmental microorganisms, including Escherichia spp., Pantoea spp., Staphylococcus spp., Botrytis spp., Tetrapisispora spp. and Pichia spp., among others. During the lab-scale fermentation, the inoculation of S. cerevisiae mostly yielded alcohols, while LAB and AAB produced volatiles associated with floral, almond and fruity notes throughout the fermentation, but AAB also produced acetic acid with a sour aroma. Similarly, the inoculation of C. metapsilosis and Bacillus spp. in 96 h fermented cacao beans yielded esters with floral aromas. This is the first report describing the role of microorganisms in volatile formation during fine-flavor cacao fermentation.

Acetobacter senegalensis Isolated from Mango Fruits: Its Polyphasic Characterization and Adaptation to Protect against Stressors in the Industrial Production of Vinegar: A Review

It has been more than a decade since Acetobacter senegalensis was isolated, identified, and described as a thermotolerant strain of acetic acid bacteria. It was isolated from mango fruits in Senegal and used for industrial vinegar production in developing countries, mainly in sub-Saharan Africa. The strain was tested during several spirit vinegar fermentation processes at relatively high temperatures in accordance with African acclimation. The upstream fermentation process had significant stress factors, which are highlighted in this review so that the fermentation process can be better controlled. Due to its high industrial potential, this strain was extensively investigated by diverse industrial microbiologists worldwide; they concentrated on its microbiological, physiological, and genomic features. A research group based in Belgium proposed an important project for the investigation of the whole-genome sequence of A. senegalensis. It would use a 454-pyrosequencing technique to determine and corroborate features that could give this strain significant diverse bioindustrial applications. For instance, its application in cocoa bean fermentation has made it a more suitable acetic acid bacterium for the making of chocolate than Acetobacter pasteurianus. Therefore, in this paper, we present a review that summarizes the current research on A. senegalensis at its microbial and genomic levels and also its specific bioindustrial applications, which can provide economic opportunities for African agribusiness.

Advantages and disadvantages of non-starter lactic acid bacteria from traditional fermented foods: Potential use as starters or probiotics

Traditional fermented foods are a significant source of starter and/or non-starter lactic acid bacteria (nsLAB). Moreover, these microorganisms are also known for their role as probiotics. The potential of nsLAB is huge; however, there are still challenges to be overcome with respect to characterization and application. In the present review, the most important steps that autochthonous lactic acid bacteria isolated from fermented foods need to overcome, to qualify as novel starter cultures, or as probiotics, in food technology and biotechnology, are considered. These different characterization steps include precise identification, detection of health-promoting properties, and safety evaluation. Each of these features is strain specific and needs to be accurately determined. This review highlights the advantages and disadvantages of nsLAB, isolated from traditional fermented foods, discussing safety aspects and sensory impact.

Impact of controlled fermentation on the volatile aroma of roasted cocoa

Abstract The study of controlled methods of cocoa fermentation on a small scale is important to assess the maintenance of heat generated in the last days of fermentation. The research aimed to study the impact of spontaneous fermentation in controlled fermentation systems on the quality and acceptability of fermented cocoa beans. A 2×3 complete factorial design used different controlled fermentation systems (jacket system, solar heater and wooden box) and pulp reduction as variables. Samples were analyzed for fermentation index and volatile aroma composition profile using Headspace-Solid Phase Microextraction (HS-SPME) and Gas Chromatography-Mass Spectrometry (GC-MS). The profile of volatile compounds is evaluated for the studied variables using a multivariate Principal Components Analysis (PCA). The results showed increasing fermentation times in the jacket system seeing that it raised the fermentation rate and accelerated it to five days of fermentation combined with pulp reduction. The PCA analysis showed differences in the chemical composition of volatile compounds that were mainly associated with the reduction of the pulping process than the type of controlled system in four days of fermentation.

Functional yeast starter cultures for cocoa fermentation

The quest to develop a performant starter culture mixture to be applied in cocoa fermentation processes started in the 20th century, aiming at achieving high‐quality, reproducible chocolates with improved organoleptic properties. Since then, different yeasts have been proposed as candidate starter cultures, as this microbial group plays a key role during fermentation of the cocoa pulp‐bean mass. Yeast starter culture‐initiated fermentation trials have been performed worldwide through the equatorial zone and the effects of yeast inoculation have been analysed as a function of the cocoa variety (Forastero, Trinitario and hybrids) and fermentation method (farm‐, small‐ and micro‐scale) through the application of physicochemical, microbiological and chemical techniques. A thorough screening of candidate yeast starter culture strains is sometimes done to obtain the best performing strains to steer the cocoa fermentation process and/or to enhance specific features, such as pectinolysis, ethanol production, citrate assimilation and flavour production. Besides their effects during cocoa fermentation, a significant influence of the starter culture mixture applied is often found on the cocoa liquors and/or chocolates produced thereof. Thus, starter culture‐initiated cocoa fermentation processes constitute a suitable strategy to elaborate improved flavourful chocolate products.

Bioprospecting of indigenous yeasts involved in cocoa fermentation using sensory and chemical strategies for selecting a starter inoculum

Cocoa fermentation is the key and most relevant process in the synthesis of aroma and flavor precursor molecules in dry beans or raw material for producing chocolate. Because this process occurs in an uncontrolled manner, the chemical and sensory quality of beans can vary and be negatively affected. One of the strategies for the standardization and improvement of the sensory quality of chocolate is the introduction of microbial starter cultures. Among these, yeasts involved in fermentation have been studied because of their pectinolytic and metabolic potential in the production of volatile compounds. This study was aimed at isolating and characterizing, both sensory and chemically, yeasts involved in cocoa fermentation that could be used as starter cultures from two agro-ecological regions for the cultivation of cocoa in Colombia. The microbiological analyses identified 22 species represented mostly by Saccharomyces cerevisiae, Wickerhamomyces anomalus and Pichia sp. The preliminary sensory analysis of eight of these species showed that Hanseniaspora thailandica and Pichia kluyveri presented sensory profiles characterized by high intensity levels of fruity notes, which could be ascribed to the production of ethyl acetate, isoamyl acetate, and 2-phenylethyl acetate.

Indigenous Yeast, Lactic Acid Bacteria, and Acetic Acid Bacteria from Cocoa Bean Fermentation in Indonesia Can Inhibit Fungal-Growth-Producing Mycotoxins

Cocoa bean fermentation is an important process in the manufacturing of cocoa products. It involves microbes, such as lactic acid bacteria, yeast, and acetic acid bacteria. The presence of mold in cocoa bean fermentation is undesired, as it reduces the quality and may produce mycotoxins, which can cause poisoning and death. Aspergillus niger is a fungus that produces ochratoxin A, which is often found in dried agricultural products such as seeds and cereals. In this study, we applied indigenous Candida famata HY-37, Lactobacillus plantarum HL-15, and Acetobacter spp. HA-37 as starter cultures for cocoa bean fermentation. We found that the use of L. plantarum HL-15 individually or in combination Candida famata HY-37, Lactobacillus plantarum HL-15, and Acetobacter spp. HA-37 as a starter for cocoa bean fermentation can inhibit the growth of A. niger YAC-9 and the synthesis of ochratoxin A during fermentation and drying. With biological methods that use indigenous Lactobacillus plantarum HL-15 individually or in combination with Candida famata HY-37 and Acetobacter spp. HA-37, we successfully inhibited contamination by ochratoxin-A-producing fungi. Thus, the three indigenous microbes should be used in cocoa bean fermentation to inhibit the growth of fungi that produce mycotoxins and thus improve the quality.

Influence of S. cerevisiae and P. kluyveri as starters on chocolate flavour

BACKGROUND

Fermented cocoa beans (Theobroma cacao L.) are a pivotal raw material for chocolate production. A cocktail yeast applied in the cocoa fermentation process can promote the formation of pleasant metabolites. Saccharomyces, Pichia and Hanseniaspora have been widely used in fermentation to improve the final product organoleptic profile, highlighting that fermentation is a critical point for chocolate flavour precursor production. This study aims to evaluate the impact of Pichia kluyveri and Saccharomyces cerevisiae strains as starter cultures on the fermentation for two cocoa hybrids, FA13 and CEPEC2002.

RESULTS

During fermentation processes, volatile organic compounds (VOCs) and protein profiles were assessed. Chocolates produced were also assessed regarding the presence of VOCs. Eighty VOCs were identified using gas chromatography coupled to mass spectrometry analysis. Mass spectrometry provided the protein profile evolution during fermentation and showed that the profiles changed with inoculation type (spontaneous versus inoculated fermentation). Chocolate obtained from FA13 inoculated with S. cerevisiae strain contained a greater amount of organics acids, being categorised as sourer than chocolate produced by spontaneous fermentation of FA13. CEPEC2002 inoculated with S. cerevisiae strain in co-culture with P. kluyveri strain generated less sour and sweeter chocolate than spontaneous fermentation only.

CONCLUSIONS

Chocolates from inoculated assays with starter cultures were more accepted by evaluators, highlighting that P. kluyveri and S. cerevisiae influence the composition of VOCs. Besides, protein profiles also changed throughout fermentation. Further investigation should be conducted to clarify protein degradation dynamics during inoculated fermentations to define which of the microbial cultures positively affect the chocolate sensory characteristics. © 2021 Society of Chemical Industry.

The Altitude of Coffee Cultivation Causes Shifts in the Microbial Community Assembly and Biochemical Compounds in Natural Induced Anaerobic Fermentations

Coffee harvested in the Caparaó region (Minas Gerais, Brazil) is associated with high-quality coffee beans resulting in high-quality beverages. We characterize, microbiologically and chemically, fermented coffees from different altitudes through target NGS, chromatography, and conventional chemical assays. The genera Gluconobacter and Weissella were dominant in coffee’s fruits from altitudes 800 and 1,000 m. Among the Eukaryotic community, yeasts were the most dominant in all altitudes. The most dominant fungal genus was Cystofilobasidium, which inhabits cold environments and resists low temperatures. The content of acetic acid was higher at altitudes 1,200 and 1,400 m. Lactic acid and the genus Leuconostoc (Pearson: 0.93) were positively correlated. The relative concentration of volatile alcohols, especially of 2-heptanol, was high at all altitudes. Bacteria population was higher in coffees from 800 m, while at 1,000 m, fungi richness was favored. The altitude is an important variable that caused shifts in the microbial community and biochemical compounds content, even in coffees belonging to the same variety and cultivated in the same region under SIAF (self-induced anaerobic fermentation) conditions. Coffee from lower altitudes has higher volatile alcohols content, while high altitudes have esters, aldehydes, and total phenolics contents.

Functional role of yeasts, lactic acid bacteria and acetic acid bacteria in cocoa fermentation processes

Cured cocoa beans are obtained through a post-harvest, batchwise process of fermentation and drying carried out on farms in the equatorial zone. Fermentation of cocoa pulp-bean mass is performed mainly in heaps or boxes. It is made possible by a succession of yeast, lactic acid bacteria (LAB) and acetic acid bacteria (AAB) activities. Yeasts ferment the glucose of the cocoa pulp into ethanol, perform pectinolysis and produce flavour compounds, such as (higher) alcohols, aldehydes, organic acids and esters. LAB ferment the glucose, fructose and citric acid of the cocoa pulp into lactic acid, acetic acid, mannitol and pyruvate, generate a microbiologically stable fermentation environment, provide lactate as carbon source for the indispensable growth of AAB, and contribute to the cocoa and chocolate flavours by the production of sugar alcohols, organic acids, (higher) alcohols and aldehydes. AAB oxidize the ethanol into acetic acid, which penetrates into the bean cotyledons to prevent seed germination. Destruction of the subcellular seed structure in turn initiates enzymatic and non-enzymatic conversions inside the cocoa beans, which provides the necessary colour and flavour precursor molecules (hydrophilic peptides, hydrophobic amino acids and reducing sugars) for later roasting of the cured cocoa beans, the first step of the chocolate-making.

A Combined Metagenomics and Metatranscriptomics Approach to Unravel Costa Rican Cocoa Box Fermentation Processes Reveals Yet Unreported Microbial Species and Functionalities

Cocoa fermentation is the first step in the post-harvest processing chain of cocoa and is important for the removal of the cocoa pulp surrounding the beans and the development of flavor and color precursors. In the present study, metagenomic and metatranscriptomic sequencing were applied to Costa Rican cocoa fermentation processes to unravel the microbial diversity and assess the function and transcription of their genes, thereby increasing the knowledge of this spontaneous fermentation process. Among 97 genera found in these fermentation processes, the major ones were Acetobacter, Komagataeibacter, Limosilactobacillus, Liquorilactobacillus, Lactiplantibacillus, Leuconostoc, Paucilactobacillus, Hanseniaspora, and Saccharomyces. The most prominent species were Limosilactobacillus fermentum, Liquorilactobacillus cacaonum, and Lactiplantibacillus plantarum among the LAB, Acetobacter pasteurianus and Acetobacter ghanensis among the AAB, and Hanseniaspora opuntiae and Saccharomyces cerevisiae among the yeasts. Consumption of glucose, fructose, and citric acid, and the production of ethanol, lactic acid, acetic acid, and mannitol were linked to the major species through metagenomic binning and the application of metatranscriptomic sequencing. By using this approach, it was also found that Lacp. plantarum consumed mannitol and oxidized lactic acid, that A. pasteurianus degraded oxalate, and that species such as Cellvibrio sp., Pectobacterium spp., and Paucilactobacillus vaccinostercus could contribute to pectin degradation. The data generated and results presented in this study could enhance the ability to select and develop appropriate starter cultures to steer the cocoa fermentation process toward a desired course.

Curing of Cocoa Beans: Fine-Scale Monitoring of the Starter Cultures Applied and Metabolomics of the Fermentation and Drying Steps

Starter culture-initiated cocoa fermentation processes can be applied to improve the quality of cured cocoa beans. However, an accurate monitoring of the microbial strains inoculated in fresh cocoa pulp-bean mass to assess their contribution to the cocoa bean curing process is still lacking. In the present study, eight different cocoa fermentation processes were carried out with Trinitario cocoa in vessels in Costa Rica to assess the contribution of two candidate yeast starter culture strains, namely Saccharomyces cerevisiae IMDO 050523 and Pichia kudriavzevii IMDO 020508, inoculated in combination with Limosilactobacillus fermentum IMDO 0611222 and Acetobacter pasteurianus IMDO 0506386. A multiphasic approach, consisting of culture-dependent selective plating and incubation, rRNA-PCR-DGGE community profiling of agar plate washes, and culture-independent high-throughput amplicon sequencing, combined with a metabolite target analysis of non-volatile and volatile organic compounds (VOCs), was performed on samples from the fermentation and/or drying steps. The different starter culture mixtures applied effectively steered the cocoa fermentation processes performed. Moreover, the use of an amplicon sequence variant (ASV) approach, aligning these ASVs to the whole-genome sequences of the inoculated strains, allowed the monitoring of these inoculated strains and their differentiation from very closely related variants naturally present in the background or spontaneous fermentation processes. Further, traits such as malolactic fermentation during the fermentation step and acetoin and tetramethylpyrazine formation during the drying step could be unraveled. Finally, the yeast strains inoculated influenced the substrate consumption and metabolite production during all starter culture-initiated fermentation processes. This had an impact on the VOC profiles of the cured cocoa beans. Whereas the P. kudriavzevii strain produced a wide range of VOCs in the cocoa pulp, the S. cerevisiae strain mostly influenced the VOC composition of the cured cocoa beans.

Co-culturing fructophilic lactic acid bacteria and yeast enhanced sugar metabolism and aroma formation during cocoa beans fermentation

Glucose and fructose are the main fermentable sugars in cocoa pulp. During fermentation, glucose is consumed within 48-72 h and fructose only after 120 h, mainly associated with the preferential use of glucose by microorganisms. In the first stage of this study, the complete genome sequence of a lactic acid bacterium with high fructose consumption capacity (Lactobacillus plantarum LPBF35) was reported. The notable genomic features of L. plantarum LPBF35 were the presence of alcohol/acetaldehyde dehydrogenase gene and improved PTS system, confirming its classification as a "facultatively" fructophilic bacterium. Subsequently, this bacterium was introduced into cocoa fermentation process in single and mixed cultures with Pediococcus acidilactici LPBF66 or Pichia fermentans YC5.2. Community composition by Illumina-based amplicon sequencing and viable counts indicated suppression of wild microflora in all treatments. At the beginning of the fermentation processes, cocoa pulp consisted of approximately 73.09 mg/g glucose and 73.64 mg/g fructose. The L. plantarum LPBF35 + P. fermentans YC5.2 process showed the lowest levels of residual sugars after 72 h of fermentation (7.89 and 4.23 mg/g, for fructose and glucose, respectively), followed by L. plantarum LPBF35 + Ped. acidilactici LPBF66 (8.85 and 6.42 mg/g, for fructose and glucose, respectively), single L. plantarum LPBF35 treatment (4.15 and 10.15 mg/g, for fructose and glucose, respectively), and spontaneous process (22.25 and 14.60 mg/g, for fructose and glucose, respectively). The positive interaction between L. plantarum LPBF35 and P. fermentans YC5.2 resulted in an improved formation of primary (ethanol, lactic acid, and acetic acid) and secondary (2-methyl-1-butanol, isoamyl acetate, and ethyl acetate) metabolites during fermentation. The primary metabolites accumulated significantly in cocoa beans fermented by P. fermentans YC5.2 + L. plantarum LPBF35, causing important reactions of color development and key flavor molecules formation. The results of this study suggest that fructophilic lactic acid bacteria and yeast is a microbial consortium that could improve sugar metabolism and aroma formation during cocoa beans fermentation.

Kluyveromyces marxianus as a Probiotic Yeast: A Mini-review

Background:

Yeasts play diverse roles in human life. Since ancient times, these micro organisms have been used to produce food products and beverages including bread and beer. Nowadays, the biotechnological products of yeast are some of the main components of commercial products.

Objective:

Some species of yeast such as Saccharomyces cerevisiae and Saccharomyces boulardii are recognized as probiotic yeast with extensive applications in the food and drug industries. However, certain species like Kluyveromyces marxianus are still not recognized as probiotic micro organisms despite their widespread industrial usage. In this study, the application of K. marxianus in preparing food and the medicinal product was reviewed in terms of its beneficial or harmful effects.

Methods:

Pub Med, Google Scholar, Scopus, and Science Direct databases were searched by using “Probiotics”, “Yeast”, and “Kluyveromyces marxianus”.

Results:

The findings suggest that K. marxianus can be recognized as a probiotic yeast species.

Conclusion:

It can be concluded that K. marxianus may be considered as a probiotic micro organism with a variety of commercial and medical applications.

Enumeration and Identification of Bacterial Spores in Cocoa Powders

ABSTRACT

The presence of bacterial spores in cocoa powders is inevitable due to the cocoa bean fermentation process, during which members of the genera Bacillus and Geobacillus are typically present. Spores are a concern in heat-treated foods when they survive heat treatments and the finished product supports germination, growth, and potentially toxin production. In this study, available methods for the enumeration of total mesophilic and thermophilic spores (TMS and TTS, respectively) were evaluated, leading to the recommendation of one global method specifically for cocoa powders. The proposed method was validated during a ring test on seven selected cocoa powders and applied during routine analyses on commercial powders. The method includes dilution of cocoa powder using buffered peptone water, heating at 80°C for 10 min for TMS and TTS counts, and heating at 100°C for 30 min for a heat-resistant (HR) spore count. Tryptic soy agar is used as a recovery medium with a maximal concentration of cocoa powder of 2.5 mg/mL (to prevent growth inhibition) and a nonnutrient agar overlay to prevent swarming of bacteria. Plates are incubated for at least 72 h at 30°C for recovery of mesophilic bacteria and 55°C for thermophilic bacteria. Suitable alternatives to specific method parameters are provided. Median values of total spore concentrations are low (<400 CFU/g for TMS and <75 CFU/g for TTS), and concentrations of HR spores are very low (<5 CFU/g). Importantly, the relation between concentrations of HR spores in cocoa powder and incidence of spoilage of heat-treated beverages containing cocoa is currently unclear. In the powders included in this study, Bacillus subtilis and Bacillus licheniformis were the predominant spore-forming species identified (49 and 39%, respectively). Both species are known for high variability in spore heat resistance. The development of reliable and sensitive molecular methods is therefore required to assess the risk of spoilage caused by spores present in cocoa powders.

HIGHLIGHTS

Replacement of Fish Meal by Solid State Fermented Lupin (Lupinus albus) Meal with Latobacillus plantarum 299v: Effect on Growth and Immune Status of Juvenile Atlantic Salmon (Salmo salar)

The aim of this study was to assess quality of SSF (Solid State Fermented) lupin with Lactobacillus plantarum 299v, and its effects (on growth, feed utilization, digestibility and immunity) of juvenile Atlantic salmon (S. salar), when used as fish meal replacer. Five experimental diets were formulated to provide 40% crude protein and 21% dietary lipid (dry matter basis) with the raw or fermented lupin meal-based protein source replacing fish meal at 15% and 30%. Triplicate groups of fish (averaging 3.53 ± 0.05 g) were fed with experimental diets for 8 weeks. Fermentation process modified nutrient profile of lupin meal and enriched it with lactic, citric and acetic acids. Fish in the FL15% group showed a higher (P < 0.05) final body weight, weight gain, FCR, SGR, and PER compared to those of C group. Apparent digestibility coefficient (ADC) of protein and Nitrogen-free extract showed a significantly higher values in FL15% experimental group, compared to those shown in C group. Fish in the FL15% group showed a higher (P<0.05) lysozyme activity and leucocyte respiratory burst compared to that shown by fish samples in the C experimental group; phagocytic activity did not record differences among experimental groups. In conclusion, replacement of fish meal by raw or fermented lupin meal did not compromise growth, apparent digestibility coefficients and immune status of juvenile Atlantic salmon and even improve fish performance when supplemented at 15%.

The Role of Yeasts in Fermentation Processes

In recent years, vessels have been discovered that contain the remains of wine with an age close to 7000 years. It is unclear whether, in ancient times, humans accidentally stumbled across fermented beverages like wine or beer, or was it a product intended as such. What is a fact is that since then, alcoholic beverages have been part of the diet and culture of many of the civilizations that have preceded us. The typical examples of beer and wine are an example of many other drinks resulting from the action of yeasts. In addition to these two beverages, various companies have developed other types of fermented foods and non-alcoholic beverages prepared in a traditional or commercial manner. The climatic conditions, the availability of raw material and the preferences of each region have conditioned and favored the maintenance of some of these products. In addition to the aforementioned traditional alcoholic beverages produced from fruits, berries, or grains, humans use yeast in the production of chemical precursors, global food processing such as coffee and chocolate, or even wastewater processing. Yeast fermentation is not only useful in food manufacturing. Its uses extend to other products of high interest such as the generation of fuel from vegetable sources.

Microorganisms during cocoa fermentation: systematic review

Introduction. Cocoa (Theobroma cacao L.) originates from Ecuador. It is one of the oldest foods in the world. The fact that cocoa is the main component in chocolate industry makes it one of the most quoted raw materials today. The chemical, physical, microbiological, and sensory properties of cocoa determine its quality and, as a result, economic and nutritional value. The research objective was to conduct a detailed analysis of cocoa fermentation process and to study the transformations this raw material is subjected to during processing. Study objects and methods. The present article introduces a substantial bibliographic review based on three databases: Science Direct, Scopus, and Medline. The scientific publications were selected according to several factors. First, they had to be relevant in terms of cocoa fermentation. Second, they were written in English or Spanish. Third, the papers were indexed in high-impact journals. The initial selection included 350 articles, while the final list of relevant publications featured only 50 works that met all the requirements specified above. Results and discussion. The main characteristics of yeasts, lactic bacteria, and acetic bacteria were analyzed together with their main parameters to describe their activities during different stages of alcoholic, lactic, and acetic fermentation. A thorough analysis of the main enzyme-related processes that occur during fermentation makes it possible to optimize the use of substrates, temperature, time, pH, acidity, and nutrients. As a result, the finished product contains an optimal concentration of volatile compounds that are formed in the beans during fermentation. The study featured the main strains of fermentation-related microorganisms, their activities, main reactions, and products. Conclusion. This study makes it possible to improve the process of fermentation to obtain beans with a better chemical composition.

Saccharomyces cerevisiae and its industrial applications

Saccharomyces cerevisiae is the best studied eukaryote and a valuable tool for most aspects of basic research on eukaryotic organisms. This is due to its unicellular nature, which often simplifies matters, offering the combination of the facts that nearly all biological functions found in eukaryotes are also present and well conserved in S. cerevisiae. In addition, it is also easily amenable to genetic manipulation. Moreover, unlike other model organisms, S. cerevisiae is concomitantly of great importance for various biotechnological applications, some of which date back to several thousands of years. S. cerevisiae's biotechnological usefulness resides in its unique biological characteristics, i.e., its fermentation capacity, accompanied by the production of alcohol and CO2 and its resilience to adverse conditions of osmolarity and low pH. Among the most prominent applications involving the use of S. cerevisiae are the ones in food, beverage -especially wine- and biofuel production industries. This review focuses exactly on the function of S. cerevisiae in these applications, alone or in conjunction with other useful microorganisms involved in these processes. Furthermore, various aspects of the potential of the reservoir of wild, environmental, S. cerevisiae isolates are examined under the perspective of their use for such applications.

Update of the list of QPS-recommended biological agents intentionally added to food or feed as notified to EFSA 10: Suitability of taxonomic units notified to EFSA until March 2019

The qualified presumption of safety (QPS) procedure was developed to provide a harmonised generic pre-evaluation to support safety risk assessments of biological agents performed by EFSA's Scientific Panels. The taxonomic identity, body of knowledge, safety concerns and antimicrobial resistance were assessed. Safety concerns identified for a taxonomic unit (TU) are, where possible and reasonable in number, reflected by 'qualifications' which should be assessed at the strain level by the EFSA's Scientific Panels. During the current assessment, no new information was found that would change the previously recommended QPS TUs and their qualifications. The list of microorganisms notified to EFSA from applications for market authorisation was updated with 47 biological agents, received between October 2018 and March 2019. Of these, 19 already had QPS status, 20 were excluded from the QPS exercise by the previous QPS mandate (11 filamentous fungi) or from further evaluations within the current mandate (9 notifications of Escherichia coli). Sphingomonas elodea, Gluconobacter frateurii, Corynebacterium ammoniagenes, Corynebacterium casei, Burkholderia ubonensis, Phaeodactylum tricornutum, Microbacterium foliorum and Euglena gracilis were evaluated for the first time. Sphingomonas elodea cannot be assessed for a possible QPS recommendation because it is not a valid species. Corynebacterium ammoniagenes and Euglena gracilis can be recommended for the QPS list with the qualification 'for production purposes only'. The following TUs cannot be recommended for the QPS list: Burkholderia ubonensis, due to its potential and confirmed ability to generate biologically active compounds and limited of body of knowledge; Corynebacterium casei, Gluconobacter frateurii and Microbacterium foliorum, due to lack of body of knowledge; Phaeodactylum tricornutum, based on the lack of a safe history of use in the food chain and limited knowledge on its potential production of bioactive compounds with possible toxic effects.

Effect of Bacterial and Yeast Starters on the Formation of Volatile and Organic Acid Compounds in Coffee Beans and Selection of Flavors Markers Precursors During Wet Fermentation

Coffee quality has recently become a high demand of coffee consumers, due to all the specialty coffees available on the market. Specialty coffees can be generated by favoring growth of some groups of microorganisms during fermentation or by using starters. Just as yeast, a variety of bacteria can be used to generate important flavor precursors. The aim of this work was to test the efficiency of coffee sterilization and adhesion of microbial cells on beans, to evaluate the effect of yeast and bacterial starters on the production of organic and volatile compounds, and selection of potential flavor marker precursors during the wet fermentation. Three yeast and six bacterial starters were inoculated in coffee beans. Coffee sterilization and microbial adhesion was observed by scanning electron microscopy (SEM). Organic compounds were detected by high performance liquid chromatography (HPLC) and volatile compounds by gas chromatography–mass spectrometry (GC–MS). Micrographs from the SEM showed that sterilization was efficient, because there were no microbial cells after autoclaving for 5 min. Also, it was observed an increase of microbial cells from 0 to 48 h of fermentation. Malic, lactic, and acetic acid were only detected in the bacterial treatments. Volatile compounds: 4-ethenyl-1,2-dimethoxybenzene, heptadecanol, 4-hydroxy-2-methylacetophenone, and 1-butanol,2-methyl were only found in yeast treatments. Guaiacol was only produced by the inoculated B. subtilis starters. In conclusion, yeast starters were better producers of volatile alcohols and bacterial starters of acid compounds. This study allowed the selection of potential flavor marker precursors, such as heptadecanol, 4-hydroxy-2-methylacetophenone, 7-methyl-4-octanol, and guaiacol.

Formation of aromatic compounds precursors during fermentation of Criollo and Forastero cocoa

There are three main genetic varieties of cocoa (Theobroma cacao L) used in chocolate making: Forastero, Trinitario and Criollo, which are distinguished by their aroma, an attribute that determines their quality. Criollo cocoa is of the highest quality and is used in the manufacture of fine chocolates because of its fruity aroma. The aroma of Criollo cocoa is defined by volatile compounds such as pyrazines and aldehydes, which are formed during roasting of the bean, from aroma precursors (reducing sugars and free amino acids) that are generated inside the bean via enzymatic reactions during fermentation; for this reason, fermentation is the most important process in the value chain. This review discusses the production of aroma precursors of Criollo and Forastero cocoa by studying the kinetics of spontaneous fermentation and the role of starter cultures to produce aroma precursors. Fine aroma precursors produced in the pulp during the fermentation phase will migrate into the bean when it's permeability is improved and then retained during the drying phase. Diffusion of aroma precursors into the cocoa bean may be possible, this process is mathematically characterized by the coefficient of molecular diffusion D, which describe the process of mass transfer via Fick's Second Law. The current state of knowledge is analyzed based on existing research and reports some gaps in the literature, suggesting future research that will be necessary for a better understanding of cocoa fermentation.

Application of lactic acid derived from food waste on pathogen inactivation in fecal sludge: a review on the alternative use of food waste

Food waste generation and disposal have led to several environmental problems, especially in developing countries. This phenomenon is partly because most cities rapidly urbanize, which results in population increase, urban settlement and waste generation. Improper management of waste has continued to create environmental problems. These problems have indeed interfered with the inadequate measures in managing other organic waste such as food waste. Food waste can be fermented and used for pathogen inactivation in fecal sludge (FS). The continual decrease in global crop production due to soil erosion, nutrient runoff and loss of organic matter has generated interest in using FS for soil amendment. However, due to the high number of pathogens in FS that are harmful to humans, FS must be treated before being used in agriculture. Thus, given the high amounts of food waste generated globally and the lactic acid potential of fermented food waste, several researchers have recently proposed the use of fermented food waste to suppress pathogens in FS. This review presents the various approaches in pathogen inactivation in FS using different types of food waste. On the basis of the literature review, the major problems associated with the generation, collection and application of food waste in pathogen inactivation in FS are discussed. Moreover, the trends and challenges that concern the applicability of each method are critically reviewed.

Microbial Ecology of Fermented Vegetables and Non-Alcoholic Drinks and Current Knowledge on Their Impact on Human Health

Fermented foods are currently experiencing a re-discovery, largely driven by numerous health benefits claims. While fermented dairy, beer, and wine (and other alcoholic fermented beverages) have been the subject of intensive research, other plant-based fermented foods that are in some case widely consumed (kimchi/sauerkraut, pickles, kombucha) have received less scientific attention. In this chapter, the current knowledge on the microbiology and potential health benefits of such plant-based fermented foods are presented. Kimchi is the most studied, characterized by primarily acidic fermentation by lactic acid bacteria. Anti-obesity and anti-hypertension properties have been reported for kimchi and other pickled vegetables. Kombucha is the most popular non-alcoholic fermented drink. Kombucha's microbiology is remarkable as it involves all fermenters described in known fermented foods: lactic acid bacteria, acetic acid bacteria, fungi, and yeasts. While kombucha is often hyped as a "super-food," only antioxidant and antimicrobial properties toward foodborne pathogens are well established; and it is unknown if these properties incur beneficial impact, even in vitro or in animal models. The mode of action that has been studied and demonstrated the most is the probiotic one. However, it can be expected that fermentation metabolites may be prebiotic, or influence host health directly. To conclude, plant-based fermented foods and drinks are usually safe products; few negative reports can be found, but more research, especially human dietary intervention studies, are warranted to substantiate any health claim.