Overexpression and secretion of AgaA7 from Pseudoalteromonas hodoensis sp. nov in Bacillus subtilis for the depolymerization of agarose

Diversity and Screening of Cellulolytic Microorganisms from Mangrove Forests, Natural Parks, Paddy Field, and Sugarcane Plantation in Panay Island, Philippines

Cellulolytic microorganisms secrete cellulase, which plays a crucial role in the conversion of lignocellulosic biomass into value-added products with diverse applications in industries, such as biofuel, healthcare, and agriculture. As the world transitions to a bioenergy future, cellulase demand is likely to expand. However, the high cost and low catalytic activity of cellulase hinder the commercialization of biorefineries. Searching for cellulase-producing microorganisms in different environments through bioprospecting can aid in broadening the range of cellulases that are currently available. Meanwhile, the cellulolytic activity of marine microorganisms remains largely unexplored, making it difficult to compare the cellulolytic activity of terrestrial and marine environments. Thus, this study aimed to investigate the diversity and activity of culturable cellulolytic microorganisms in four terrestrial and three marine sites within Panay Island, Philippines. The results showed that the cellulolytic microbial load was tenfold higher in the terrestrial sites than in the marine sites, possibly due to the dynamic mangrove environment. Out of the 42 isolates with a high cellulolytic index (CI) of ≥3.0, 36 were from terrestrial and 6 from marine habitats. The CMCase, Avicelase, and FPase activities were then tested on the 18 isolates with the highest CI. It was observed that many isolates had a high CI, but few exhibited high enzyme activities. Marine isolates showed higher CMCase and Avicelase activities, with comparable FPase activity to their terrestrial counterparts. Isolates S1ACP6B from a sugarcane field and MS1OMP2A from a mangrove site exhibited the highest cellulase activities at 0.41 and 0.29 U/mg, respectively, and were identified as Enterobacter roggenkampii and Rhodococcus erythropolis, respectively. Among the 18 identified isolates, three are resistant to chloramphenicol and three isolates are potentially new species of Halomonas sp. MS1ACP1B, Albirhodobacter sp. MP2ACP3B, and Saccharomycetaceae sp. B1CZP10A. Overall, this study provides an insight on the composition of cellulolytic microbial load and their activities among various habitats.

Marine enzymes: Classification and application in various industries

Oceans are regarded as a plentiful and sustainable source of biological compounds. Enzymes are a group of marine biomaterials that have recently drawn more attention because they are produced in harsh environmental conditions such as high salinity, extensive pH, a wide temperature range, and high pressure. Hence, marine-derived enzymes are capable of exhibiting remarkable properties due to their unique composition. In this review, we overviewed and discussed characteristics of marine enzymes as well as the sources of marine enzymes, ranging from primitive organisms to vertebrates, and presented the importance, advantages, and challenges of using marine enzymes with a summary of their applications in a variety of industries. Current biotechnological advancements need the study of novel marine enzymes that could be applied in a variety of ways. Resources of marine enzyme can benefit greatly for biotechnological applications duo to their biocompatible, ecofriendly and high effectiveness. It is beneficial to use the unique characteristics offered by marine enzymes to either develop new processes and products or improve existing ones. As a result, marine-derived enzymes have promising potential and are an excellent candidate for a variety of biotechnology applications and a future rise in the use of marine enzymes is to be anticipated.

The multifunctionality of expression systems in Bacillus subtilis: Emerging devices for the production of recombinant proteins

Bacillus subtilis is a successful host for producing recombinant proteins. Its GRAS (generally recognized as safe) status and its remarkable innate ability to absorb and incorporate exogenous DNA into its genome make this organism an ideal platform for the heterologous expression of bioactive substances. The factors that corroborate its value can be attributed to the scientific knowledge obtained from decades of study regarding its biology that has fostered the development of several genetic engineering strategies, such as the use of different plasmids, engineering of constitutive or double promoters, chemical inducers, systems of self-inducing expression with or without a secretion system that uses a signal peptide, and so on. Tools that enrich the technological arsenal of this expression platform improve the efficiency and reduce the costs of production of proteins of biotechnological importance. Therefore, this review aims to highlight the major advances involving recombinant expression systems developed in B. subtilis, thus sustaining the generation of knowledge and its application in future research. It was verified that this bacterium is a model in constant demand and studies of the expression of recombinant proteins on a large scale are increasing in number. As such, it represents a powerful bacterial host for academic research and industrial purposes.

Antimicrobial Peptides from Plants: A cDNA-Library Based Isolation, Purification, Characterization Approach and Elucidating Their Modes of Action

Even in a natural ecosystem, plants are continuously threatened by various microbial diseases. To save themselves from these diverse infections, plants build a robust, multilayered immune system through their natural chemical compounds. Among the several crucial bioactive compounds possessed by plants’ immune systems, antimicrobial peptides (AMPs) rank in the first tier. These AMPs are environmentally friendly, anti-pathogenic, and do not bring harm to humans. Antimicrobial peptides can be isolated in several ways, but recombinant protein production has become increasingly popular in recent years, with the Escherichia coli expression system being the most widely used. However, the efficacy of this expression system is compromised due to the difficulty of removing endotoxin from its system. Therefore, this review suggests a high-throughput cDNA library-based plant-derived AMP isolation technique using the Bacillus subtilis expression system. This method can be performed for large-scale screening of plant sources to classify unique or homologous AMPs for the agronomic and applied field of plant studies. Furthermore, this review also focuses on the efficacy of plant AMPs, which are dependent on their numerous modes of action and exceptional structural stability to function against a wide range of invaders. To conclude, the findings from this study will be useful in investigating how novel AMPs are distributed among plants and provide detailed guidelines for an effective screening strategy of AMPs.

Advances in agaro-oligosaccharides preparation and bioactivities for revealing the structure-function relationship

Agaro-oligosaccharides originating from red algae have attracted increasing attention in both basic theoretical research and applied fields due to their excellent bioactivities, which indicates the wide prospects of agaro-oligosaccharides for application in the food, pharmaceutical and cosmetic industries. Thus, a considerable number of studies regarding functional agaro-oligosaccharides preparation as well as the bioactivities exploration have been carried out. Based on these studies, this review first introduced different methods that have been used in agar extraction from red algae, and further provided research progress on arylsulfatase. Then, different methods used for agaro-oligosaccharides production were summarized. Moreover, the abundant bioactivities of agaro-oligosaccharides were described in detail. Finally, this review has discussed current research problems and further provided critical aspects, which may be helpful for revealing the structure-function relationship of agaro-oligosaccharide.

Production of Neoagaro-Oligosaccharides With Various Degrees of Polymerization by Using a Truncated Marine Agarase

Bioactivities, such as freshness maintenance, whitening, and prebiotics, of marine neoagaro-oligosaccharides (NAOS) with 4-12 degrees of polymerization (DPs) have been proven. However, NAOS produced by most marine β-agarases always possess low DPs (≤6) and limited categories; thus, a strategy that can efficiently produce NAOS especially with various DPs ≥8 must be developed. In this study, 60 amino acid residues with no functional annotation result were removed from the C-terminal of agarase AgaM1, and truncated recombinant AgaM1 (trAgaM1) was found to have the ability to produce NAOS with various DPs (4-12) under certain conditions. The catalytic efficiency and stability of trAgaM1 were obviously lower than the wild type (rAgaM1), which probably endowed trAgaM1 with the ability to produce NAOS with various DPs. The optimum conditions for various NAOS production included mixing 1% agarose (w/v) with 10.26 U/ml trAgaM1 and incubating the mixture at 50°C in deionized water for 100 min. This strategy produced neoagarotetraose (NA4), neoagarohexaose (NA6), neoagarooctaose (NA8), neoagarodecaose (NA10), and neoagarododecaose (NA12) at final concentrations of 0.15, 1.53, 1.53, 3.02, and 3.02 g/L, respectively. The NAOS served as end-products of the reaction. The conditions for trAgaM1 expression in a shake flask and 5 L fermentation tank were optimized, and the yields of trAgaM1 increased by 56- and 842-fold compared with those before optimization, respectively. This study provides numerous substrate sources for production and activity tests of NAOS with high DPs and offers a foundation for large-scale production of NAOS with various DPs at a low cost.

Two antimicrobial genes from Aegilops tauschii Cosson identified by the Bacillus subtilis expression system

Antimicrobial genes play an important role as a primary defense mechanism in all multicellular organisms. We chose Bacillus subtilis as a target pathogen indicator and transferred the Aegilops tauschii Cosson cDNA library into B. subtilis cells. Expression of the candidate antimicrobial gene can inhibit B. subtilis cell growth. Using this strategy, we screened six genes that have an internal effect on the indicator bacteria. Then, the secreted proteins were extracted and tested; two genes, AtR100 and AtR472, were found to have strong external antimicrobial activities with broad-spectrum resistance against Xanthomonas oryzae pv. oryzicola, Clavibacter fangii, and Botrytis cinerea. Additionally, thermal stability tests indicated that the antimicrobial activities of both proteins were thermostable. Furthermore, these two proteins exhibited no significant hemolytic activities. To test the feasibility of application at the industrial level, liquid fermentation and spray drying of these two proteins were conducted. Powder dilutions were shown to have significant inhibitory effects on B. cinerea. Fluorescence microscopy and flow cytometry results showed that the purified protein impaired and targeted the cell membranes. This study revealed that these two antimicrobial peptides could potentially be used for replacing antibiotics, which would provide the chance to reduce the emergence of drug resistance.

Overexpression and characterization of a novel GH16 β-agarase (Aga1) from Cellulophaga omnivescoria W5C

OBJECTIVE

To identify and characterize a new β-agarase from Cellulophaga omnivescoria W5C capable of producing biologically-active neoagarooligosaccharides from agar.

RESULTS

The β-agarase, Aga1, has signal peptides on both N- and C-terminals, which are involved in the type IX secretion system. It shares 75% protein sequence identity with AgaD from Zobellia galactanivorans and has a molecular weight of 54 kDa. Biochemical characterization reveals optimum agarolytic activities at pH 7-8 and temperature 30-45 °C. Aga1 retains at least 33% activity at temperatures lower than the sol-gel transition state of agarose. Metal ions are generally not essential, but calcium and potassium enhance its activity whereas iron and zinc are inhibitory. Finally, hydrolysis of agarose with Aga1 yields neoagarotetraose, neoagarohexaose, and neoagarooctaose.

CONCLUSIONS

Aga1 displays unique traits such as moderate psychrophilicity, stability, and synergy with other agarases, which makes it an excellent candidate for biosynthetic production of neoagarooligosaccharides from agar.

Extracellular expression of agarase rAgaM1 in Bacillus subtilis and its ability for neoagaro-oligosaccharide production

An agarase gene (agaM1) was cloned, expressed and characterized by using Escherichia coli as host strain, revealing the outstanding properties of recombinant AgaM1 (rAgaM1) in agarose degradation and neoagaro-oligosaccharides (NAs) production in our previous work. In current study, agaM1 was extracellularly expressed in Bacillus subtilis, and we aim to assess the ability of the supernatant of recombinant B. subtilis fermentation broth containing rAgaM1 to degrade agarose without protein purification, which would save the cost of purification and avoid the activity loss during purification. The pH and temperature optima for the supernatant were 7.0 and 50 °C, respectively. The supernatant containing rAgaM1 has outstanding stability against 40 °C and 50 °C. Besides, we detailedly studied the possible influence factors of rAgaM1 expression in the supernatant, including pH, temperature, isopropyl β-D-thiogalactoside (IPTG) concentration, initial optical density at a wavelength of 600 nm (OD₆₀₀ ), and induction time, and the optimum conditions for rAgaM1 expression by B. subtilis were confirmed. Moreover, the supernatant was able to produce NAs by using the Gracilaria lemaneiformis, whose cells were broken by autoclaving, as substrate, and a total of 1.41 µmol ml^-1 of NA, including neoagarotetraose and neoagarohexaose, was produced after degradation for 48 h. This ability could save the cost of substrates in NA production, although the method requires a further study. Our results reveal that the NAs with great potential in food and pharmaceutical industries could be inexpensive to make by the supernatant containing rAgaM1 of B. subtilis fermentation broth in the foreseeable future.

Identification and characterization of a thermostable endolytic β-agarase Aga2 from a newly isolated marine agarolytic bacteria Cellulophaga omnivescoria W5C

Research on the enzymatic breakdown of seaweed-derived agar has recently gained attention due to the progress in green technologies for marine biomass utilization. The enzymes known as agarases catalyze the cleavage of glycosidic bonds within the polysaccharide. In this study, a new β-agarase, Aga2, was identified from Cellulophaga omnivescoria W5C. Aga2 is one of four putative agarases from the W5C genome, and it belongs to the glycoside hydrolase 16 family. It was shown to be exclusive to the Cellulophaga genus. Agarase activity assays showed that Aga2 is an endolytic-type β-agarase that produces tetrameric and hexameric neoagaro-oligosaccharides, with optimum activity at 45°C and pH 8.0. Zinc ions slightly enhanced its activity while manganese ions had inhibitory effects even at very low concentrations. Aga2 has a K_m of 2.59mgmL^-1 and V_max of 275.48Umg^-1. The K_cat is 1.73×10²s^-1, while the K_cat/K_m is 8.04×10⁶s^-1M^-1. Aga2 also showed good thermostability at 45°C and above, and retained >90% of its activity after repeated freeze-thaw cycles. Bioinformatic analysis of its amino acid sequence revealed that intrinsic properties of the protein (e.g. presence of certain dipeptides and the relative volume occupied by aliphatic amino acids) and tertiary structural elements (e.g. presence of salt bridges, hydrophobic interactions and H-bonding) contributed to its thermostability.