Applied Microbiology: Open Access
Open Access

Activities of Microbial Groups During Anaerobic Digestion

Cantro Datta^{* *}Correspondence: Cantro Datta, Department of Pathogens, University of Calgary, Alberta, Canada, Email:

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Description

Microbial consortiums efficiently breakdown complex biopolymers contained in municipal solid waste's organic content. Microbial communities break down resistant polymers and produce fermentation products such as methane during anaerobic digestion by producing enzymes and dividing work. However, microbial communities continue to be underused for waste degradation because it is difficult to quantify and predict microbial interactions during waste breakdown, particularly when culture conditions change dramatically during anaerobic digestion. This study highlights current advances and potential in growing natural and artificial consortia for OFMSW hydrolysis, including how enzymes breakdown resistant substrates and the important parameters that influence microbial interactions and culture stability.

Methods for measuring substrate deterioration are also discussed, and we show the importance of enhanced uniformity to allow comparisons across diverse settings. Microbial communities and their enzymes are important players in carbon cycling because they break down and convert carbon in the environment, the human gut, and are frequently used in industrial biofermentations. Anaerobic digesters, for example, are used to create biogas through the breakdown of mixed waste materials. This biogas may subsequently be transformed into chemicals, motor fuels, and power. The Organic Fraction of Municipal Solid Waste (OFMSW) is a waste source that is widely employed in anaerobic digesters because it comprises polymers found in food waste (pectin), paper and cardboard (cellulose), wood (lignocellulose), and plastics. Many of these materials, such as cellulose, lignocellulose (composed primarily of cellulose, hemicellulose, and lignin), and plastics, are highly recalcitrant and necessitate the collaboration of specialised microbes and secreted enzymes to efficiently degrade them into substrates for biofermentation. There is a significant need to deploy microbial communities on an industrial scale for bioproduction applications, however microbial communities are frequently unexpected and unstable, particularly in large-scale fermentations. Natural microbial consortia are complicated and ambiguous, resembling a black box. Because crucial determinants that control microbial behaviour and composition are unknown, modelling and engineering potential are limited.

While metagenomics can aid in determining the composition of natural consortia, it is difficult to capture all bacteria present since the rarest ones sometimes elude identification through sequencing. Furthermore, metagenomic sequencing does not capture the activities of detected bacteria correctly. Engineered, or synthetic, consortia, on the other hand, are completely described communities that are defined here as consortia formed by merging separate microbial strains into a single culture. Despite being completely specified, these manufactured communities are less stable than natural consortia, with normal member attrition over time. Still, when it comes to bioproduction applications, microbial communities outperform monocultures because they are more adaptable to environmental changes, have higher output, and distribute metabolic burden between members. The four major processes of anaerobic digestion are catalysed by microbes (hydrolysis, acidogenesis, acetogenesis and methanogenesis). Many microorganisms release enzymes that degrade polymers extracellularly into simpler substrates that can later be eaten. During the hydrolysis stage of anaerobic digestion, for example, anaerobic bacteria such as Clostridium thermocellum commence the breakdown process by generating carbohydrate active enzymes (CAZymes), which include esterases. To breakdown the different polymers found in OFMSW, hydrolytic bacteria release a vast repertoire of enzymes such as pectinases, cellulases, hemicellulases, and even ligninmodifying enzymes.

Pectinases generated by bacteria such as Bacillus spp. include polygalacturonase, pectin, and pectate lyase. Cellulases are divided into three types, which are glucosidases, endoglucanases, and exoglucanases. Along with cellulases and lignin-modifying enzymes, hemicellulases such as xylanases and -Larabinofuranosidases aid in the breakdown of lignocellulosic materials. Prokaryotes such as Clostridium spp. and Fibrobacter spp. are prominent cellulose and hemicellulose degraders. Anaerobic fungi, which generate a variety of CAZymes and promote biomass breakdown in the guts of big herbivores and presumably other anaerobic settings, have recently been identified as essential participants in lignocellulose degradation.

Plastics are another important component of OFMSW, and possibly the most obstinate. While the synthetic character of these materials distinguishes them from the other components, Chen et al. indicated that due to structural similarities between biological lignin and plastics, lignin breakdown may give insight into plastic degradation. Plastics can be partially broken down by lignin-modifying enzymes such as lignin peroxidase, manganese peroxidase, and laccase. Carboxylic ester hydrolases have also been linked to plastic deterioration. White rot fungi are lignindegrading experts and provide sources for these enzymes that might be useful in this field. Nonetheless, there is a significant need to uncover (or build) enzymes capable of degrading plastics on a wide scale, and lignin-modifying enzymes may give a good starting point. Microbial communities for waste degradation are underused, in part owing to difficulties in adjusting environmental conditions and a lack of knowledge of complicated microbial interactions.

Further use of microbial consortia becomes conceivable when these interactions are better understood and circumstances are tuned. Natural and designed consortia will both play important roles in new technologies, notably in identifying elements related to enhancing consortia stability and productivity. Microbial communities' potential as waste degraders and makers of useful metabolites will grow as they are more understood and maximised, both in anaerobic digestion and in other industrial processes.