A set of simple methods for detection and extraction of laminarinase

Surfactin: a novel Aphis gossypii killing surfactin produced by Bacillus australimaris TRM82479 of Taklamakan Desert origin

Introduction

The cotton aphid Aphis gossypii poses a global, serious threat to cotton yield and quality. Although chemical pesticides are effective, pollution and resistance are increasingly prominent, making development of new biopesticides a priority in the context of green agricultural development.

Methods

Given that reports on the activity of surfactins against A. gossypii are limited, here, 107 Bacillus strains isolated from the extreme environment of the Chinese Taklamakan Desert were screened for insecticidal activity against A. gossypii using the leaf-dip method. Active strains were characterized by morphological observation, 16S rRNA gene sequencing, and phylogenetic analysis. Secondary metabolite synthesis genes were identified by whole-genome sequencing and antiSMASH analysis.

Results

B. australimaris strain TRM82479 showed 75.00% 48-h mortality against A. gossypii. An antiSMASH analysis showed that this strain contains several gene clusters related to the synthesis of nonribosomal peptide (NRP) fengycin and lichenysin lipopeptide analogs. Cluster 1 has the highest similarity of 52% with the fengycin synthesis gene cluster, and Cluster 8 has the highest similarity of 92% with the lichenysin synthesis gene cluster. It is inferred that B. australimaris strain can produce lipopeptide analogs distinct from fengycin and lichenysin, so we isolated and identified its NRPs. The results showed that surfactin is the main insecticidal substance, with an LC50 of 0.857 mg/mL and an LC95 of 4.350 mg/mL against cotton aphids in aqueous solution. The results of the zebrafish acute toxicity experiment showed that surfactins are low-toxic to fish, indicating good biological safety.

Discussion

This study not only provides new strain resources for cotton aphid control but also demonstrates the potential of surfactins as biopesticides, laying a foundation for their future agricultural application.

A Review on Bacteriocin Extraction Techniques from Lactic Acid Bacteria

Lactic acid bacteria (LAB) are widely known for the production of secondary metabolites such as organic acids and other bioactive compounds such as bacteriocins. Finding a broad application in food and healthcare, bacteriocins have received increased attention due to their inherent antimicrobial properties. However, the extraction of bacteriocins is often plagued with low yields due to the complexity of the extraction processes and the diversity of bacteriocins themselves. Here, we review the current knowledge related to bacteriocin extraction on the different extraction techniques for isolating bacteriocins from LAB. The advantages and disadvantages of each technique will also be critically appraised, taking into account factors such as extraction efficiency, scalability and cost-effectiveness. This review aims to guide researchers and professionals in selecting the most suitable approach for bacteriocin extraction from LAB by illuminating the respective advantages and limitations of various extraction techniques.

Antibiotic resistance profiling and valorization of food waste streams to starter culture biomass and exopolysaccharides through fed-batch fermentations

The present study evaluated antibiotic resistance (ABR) in bacteria isolated from different food wastes viz., meat slaughterhouses, dairy and restaurants. About 120 strains isolated from the food waste were subjected to ABR screening. More than 50% of all the strains were resistant to Vancomycin, Neomycin and Methicilin, which belong to third-generation antibiotics. Two lactic acid bacteria (LAB) free of ABR were chosen to be used as starter cultures in media formulated from food waste. Food waste combination (FWC-4) was found to be on par with the nutrient broth in biomass production. The non-ABR LAB strains showed excellent probiotic properties, and in the fed-batch fermentation process, adding a nitrogen source (soya protein) enhanced the microbial biomass (3.7 g/l). Additionally, exopolysaccharide production was found to be 2.3 g/l. This study highlights the ABR incidence in food waste medium and its economic advantage for starter culture biomass production.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-022-01222-9.

Cold-Active Lipases and Esterases: A Review on Recombinant Overexpression and Other Essential Issues

Cold environments characterised by diverse temperatures close to or below the water freezing point dominate about 80% of the Earth's biosphere. One of the survival strategies adopted by microorganisms living in cold environments is their expression of cold-active enzymes that enable them to perform an efficient metabolic flux at low temperatures necessary to thrive and reproduce under those constraints. Cold-active enzymes are ideal biocatalysts that can reduce the need for heating procedures and improve industrial processes' quality, sustainability, and cost-effectiveness. Despite their wide applications, their industrial usage is still limited, and the major contributing factor is the lack of complete understanding of their structure and cold adaptation mechanisms. The current review looked at the recombinant overexpression, purification, and recent mechanism of cold adaptation, various approaches for purification, and three-dimensional (3D) crystal structure elucidation of cold-active lipases and esterase.

Benchmarking a Microfluidic-Based Filtration for Isolating Biological Particles

Isolating particles from complex fluids is a crucial approach in multiple fields including biomedicine. In particular, biological matrices contain a myriad of distinct particles with different sizes and structures. Extracellular vesicles (EVs), for instance, are nanosized particles carrying vital information from donor to recipient cells, and they have garnered significant impact on disease diagnostics, drug delivery, and theranostics applications. Among all the EV types, exosome particles are one of the smallest entities, sizing from 30 to 100 nm. Separating such small substances from a complex media such as tissue culture and serum is still one of the most challenging steps in this field. Membrane filtration is one of the convenient approaches for these operations; yet clogging, low-recovery, and high fouling are still major obstacles. In this study, we design a two-filter-integrated microfluidic device focusing on dead-end and cross-flow processes at the same time, thereby minimizing any interfering factors on the recovery. The design of this platform is also numerically assessed to understand pressure-drop and flow rate effects over the procedure. As a model, we isolate exosome particles from human embryonic kidney cells cultured in different conditions, which also mimic complex fluids such as serum. Moreover, by altering the flow direction, we refresh the membranes for minimizing clogging issues and benchmark the platform performance for multitime use. By comprehensively analyzing the design and operation parameters of this platform, we address the aforementioned existing barriers in the recovery, clogging, and fouling factors, thereby achieving the use of a microfluidic device multiple times for bio-nanoparticle isolation without any notable issues.

No Solid Colloidal Carriers: Aspects Thermodynamic the Immobilization Chitinase and Laminarinase in Liposome

The present review describes the basic properties of colloidal and vesicular vehicles that can be used for immobilization of enzymes. The thermodynamic aspects of the immobilization of enzymes (laminarinase and chitinase) in liposomes are discussed. These systems protect enzymes against environmental stress and allow for a controlled and targeted release. The diversity of colloidal and vesicular carriers allows the use of enzymes for different purposes, such as mycolytic enzymes used to control phytopathogenic fungi.

Simple Methods for the Preparation of Colloidal Chitin, Cell Free Supernatant and Estimation of Laminarinase

Colloidal chitin (CC) is a common substrate used in research work involving chitin-active enzymes (chitinases). Cell free supernatant (CFS) is prepared from fermented broth. Preparation of CC and CFS usually involve large amounts of liquid, which must be separated from the solids. This necessitates the use of a large volume centrifugation facility, which may not be accessible to everyone. Filtration is a viable alternative to centrifugation, and several filter elements are described in the literature. Each of those elements has its own set of disadvantages like non-availability, high cost, fragility, and non-reusability. Here we describe the use of lab coat clothing material (LCCM) for the preparation of CC and CFS. For filtration purposes, the LCCM was found to be functional, rugged, reusable, and cost-effective. Also described here is a new method for the estimation of laminarinase using a laminarin infused agarose gel plate. An easily available optical fabric brightener (OFB) was used as a stain for the agarose plate. The laminarin infused agarose plate assay is simple, inexpensive, and was found to be impervious to high amounts of ammonium sulfate (AS) in enzyme precipitates.