Cocoa seed fermentation involves a well-stabilized succession of microbial processes and the action of enzymes. Microorganisms (yeast, lactic acid bacteria, and acetic acid bacteria) play a critical role in cacao fermentation by degrading mucilage pulp by producing a stabilized succession of enzymatic reactions that contribute to its quality. Nowadays, the majority of cacao fermentation practiced in our planet is in the traditional form to produce aroma flavor. The art of using starter culture to substitute naturally occurring microorganisms in cacao fermentation is crucial for the development of the aroma and flavor of cacao for sustainable uniformity and quality improvement and unique cacao flavor development. In this sense, this review presents an overview of cacao fermentation process and its impacts on quality, starter culture and microorganisms involved in cacao fermentation process, cacao bioactive compounds and its health benefits. Moreover, the research perspectives needed and the advance made in terms of fermentation process in order to reduce fermentation period are reviewed.

Bacillus licheniformis is a characteristic Gram-positive bacterium originally found in soil. This microorganism has long been utilised as a workhorse for production of industrial enzymes or high value-added chemicals. With ever-increasing understanding on this strain and the maturation of the genetic technique, important advances have recently been made in developing B. licheniformis as an excellent chassis cell for synthetic biology. Here, we provide an overview of updated understanding on genome information, anaerobic metabolism, industrial applications of this strain. The state-of-art B. licheniformis genetics, especially its synthetic biology advances in biosensor, expression system and artificial metabolic pathways are illustrated. Finally, perspectives are offered for the limitations and challenges to be addressed to improve B. licheniformis as microbial cell factories.

Laccases are versatile enzymes that belong to the multi-copper oxidase family. This enzyme has several biotechnological applications because of its ablilty to oxidize a wide range of phenolic and non-phenolic substrates. However, their large-scale applicability in bioremediation and water treatment is hindered by high salt content and extreme pH values of the polluted media which also affects the stability, recovery and recycling of laccase. Apart from some bacteria, laccase is abundantly present in several lignin-degrading white-rot fungi viz. Ascomycetes, Deuteromycetes, and Basidiomycetes. Recently, laccase has been employed in the development of biosensors as a medical diagnostic tool, biofuel cells, and in bioremediation purpose to remove herbicides, pesticides, and some toxic chemicals from the soil. However, most of the enzymes including laccase are normally unstable and susceptible to lose their activity over time. This might be avoided by maintaining the activity and lengthening the enzyme's lifespan through the use of appropriate immobilization procedures. The potential of laccase immobilized biocathodes for dye decolorization in microbial fuel cells has recently been studied. Immobilized laccase nanoparticles have potential uses as biocatalyst in the bioremediation of pollutants. In addition, advanced research considering microbial laccase has been conducted for its heterologous expression along with in silico protein engineering to attain maximum enzyme activity which can be potentially applied in different biotechnological sectors. Patent related to laccase also implied that this enzyme can be used as suitable catalyst for the production of promising anti-cancer drugs and even as a significant ingredient in cosmetics.

Vibrio harveyi is a Gram-negative, rod-shaped, polar flagellate, facultatively anaerobic, halophilic, bioluminescent marine bacteria that belongs to the family of Vibrionaceae, class, Gammaproteobacteria. This pathogenic organism is responsible for various diseases of vertebrates and invertebrates in marine habitats, including shrimp aquaculture. Various symptoms like lesions, gastroenteritis, skin ulcers, eye lesions, and tail rot have been observed due to V. harveyi infection. The pathogenicity mechanism of V. harveyi involves endotoxin lipopolysaccharide, extracellular proteases, and bacteriophage interaction. Hemolysin genes encoded extracellular hemolysin-like phospholipase B toxin could inactivate fish species via the caspase inactivation pathway, ultimately leading to apoptosis. In addition, VBNC (viable but nonculturable) cells are another basis of vibriosis outbreaks in the shrimp aquaculture sector. The extensive amount of antibiotic use promotes the generation of multidrug-resistant strains. Therefore, as an alternative strategy to combat V. harveyi infection, bacteriophages are utilized as a biocontrol agent. However, there is a lack of research on the immobilization and development of encapsulation strategies of V. harveyi-infecting bacteriophages which need to be studied further. In conclusion, the pathogenicity of V. harveyi and its biocontrol by bacteriophages has been documented in this review.

Cholesterol and phytosterols can be served as the substrates for Actinobacteria to produce the precursors used in the synthesis of steroidal medicines. Cytochrome P450s from CYP125 and CYP142 families initiates the metabolism of cholesterol and/or phytosterols. In this study, we demonstrate the functional redundancy and substrate preference of five cytochrome CYP125s and CYP142s by the unmarked cyp genes deletion strains of Mycobacterium neoaurum NRRL B-3805. CYP125-3 was found to be responsible for the catalytic hydroxylation of both cholesterol and the C24-branched side-chains of phytosterols, while CYP142-2 can only oxidize cholesterol and/or cholest-4-en-3-one. The strain harboring the CYP125-3 produced 6.47 g l^− 1 and 5.13 g l^− 1 of 4-androstene-3,17-dione (AD) when 15 g l^− 1 cholesterol or 17.5 g l^− 1 phytosterols used, respectively. While, the strain harboring the CYP142-2 produced 7.10 g l^− 1 AD when 15 g l^− 1 cholesterol used. The other three cytochrome P450s have a smaller contribution for the degradation of cholesterol and phytosterols. CYP125-3 has the hydroxylation activity on more substrates than that of CYP142-2. This study provided possible guidance to improve the efficiency of AD and other metabolites production from different kinds of sterols by the genetic manipulation.

Menaquinone-7 (MK-7) has an important role in preventing diseases such as cardiovascular disease and osteoporosis. In this study, a combination strategy of strain improvement and medium optimization is investigated to increase MK-7 production in Bacillus amyloliquefaciens. Conventional breeding method was first used to modify the biosynthetic pathway to construct a MK-7 high-producing strain by atmospheric and room temperature plasma mutagenesis and protoplast fusion. The resulted strain Ba-4 with resistance to sulfaguanidine, 1-hydroxy-2-naphthoic acid, menadione, 2-deoxy-d-glucose and rifampicin as well as sensitive to β-fluoropyruvate produced 73.57 ± 1.61 mg/L of MK-7, which was 1.36 times more than that of the parent strain H.β.D.R.-5 (i.e., 31.12 ± 1.40 mg/L). Subsequently, single-factor optimization and response surface methodology (RSM) were used to optimize the medium components for increasing MK-7 production by strain Ba-4. Strain Ba-4 produced 90.43 ± 1.32 mg/L of MK-7 under the single-factor optimized medium. Moreover, the results of response surface methodology indicated that glycerol, soy peptone and Tween-80 had significant effects on MK-7 production, and the highest MK-7 production (i.e., 95.03 ± 1.01 mg/L) was obtained under the optimized medium, which was 0.29 times higher than that of the initial medium. These results confirmed that the conventional breeding methods and fermenter control system are effective strategies in improving MK-7 production by B. amyloliquefaciens.

Bacillomycin D is a nonribosomal peptide produced by Bacillus amyloliquefaciens fmbJ. In this study, the biosynthesis of bacillomycin D was mediated by replacing the intermodule donor, acceptor, and communication-mediating (COM) domain pairs and introducing the COM domain between the surfactin subunits. Both the homologous donor and the COM domain pair replacement strains eliminated the selective barrier of the original COM domain pair to a certain extent, resulting in a more flexible hybrid biosynthesis system that provides simultaneous biosynthesis of different lipopeptide products. The synthesis of bacillomycin D in the homologous acceptor replacement strains was barely affected. The COM domains between the surfactin subunits cannot establish efficient communication between the bacillomycin D modules. In conclusion, the COM domains compatibility between the bacillomycin D modules are extremely strong, and the conserved amino acid residues in the acceptor domain are an important part of module–module interactions and efficient communication during bacillomycin D synthesis.

Given the environmental pollution caused by petroleum-based plastics, finding alternative substitutes for sustainability has become critical. Polyhydroxybutyrate (PHB), a storage food material that is accumulated by several bacteria, is biodegradable, safe, environment friendly and comparable to conventional plastics. However, scale-up is an issue due to high production cost. Substrate replacement using renewable, plentiful, sustainable and low-cost carbon sources derived from industrial waste facilitates waste reduction, while also enabling the synthesis of value-added products. In this context, inexpensive pulp and paper industrial waste as carbon source was exploited for production of PHB by using previously isolated (Source: hot springs of Manikarn, Himachal Pradesh, India) thermophilic bacteria Bacillus sonorensis NAM5 under optimized conditions in a fermenter. Production was done in a fermenter under optimized conditions (72 h of incubation at 50 °C temperature and 7 pH) to enhance the accumulation of PHB. The bacterial strain was able to produce 5.28 ± 0.11 g L⁻¹ after 72 h of growth without any carbon and nitrogen source supplementation to the industrial effluent. The culture accumulated 66% PHB of cell dry weight (CDW). The produced polymer was characterized through FTIR, NMR and TGA. Additionally, bacteria-treated industrial wastewater was used for phytotoxicity assay on agriculturally important crops such as wheat, maize and mung, which exhibited considerable difference in growth parameters.