Production and purification of bacteriocin from Leuconostoc lactis SM 2 strain

Soft rot of postharvest pepper: bacterial pathogen, pathogenicity and its biological control using Lactobacillus farciminis LJLAB1

BACKGROUND

Soft rot is the most important bacterial disease of postharvest pepper during storage and transportation. The main objectives of this study were to investigate the bacterial pathogen species causing pepper soft rot and seek for an antagonistic bacterium to control this disease.

RESULTS

Pathogens Pectobacterium carotovorum, Enterobacter sp., Klebsiella sp., Pseudomonas sp. and Bacillus sp. were verified to be the causes of soft rot which were isolated from rotten peppers. Among them, P. carotovorum had the highest prevalence, including P. carotovorum subsp. carotovorum (Pcc) and P. carotovorum subsp. brasilisesis (Pcb). The result of pathogenicity analysis showed that Pcb Jm2 had strong pathogenicity at 25 °C even at a cell concentration of 103  CFU mL-1 . Its pathogenicity decreased at 4 °C. Multiple pathogenic factors were identified in the draft genome of Pcb Jm2, including cellulase, pectinase, pectin methylesterase, pectinesterase, pectin lyase, polygalacturonase and so forth. Further, the disease control ability of Lactobacillus farciminis LJLAB1 was investigated. The cell-free supernatant (CFS) and crude bacteriocin of L. farciminis LJLAB1 had good antibacterial activities to Pcb Jm2 in vitro, but CFS exhibited a better disease control effect in vivo. CFS treatment prevented the damage of pepper epidermal structure caused by Pcb Jm2, and 99.26% of pathogen cells on pepper were killed by it. Moreover, CFS treatment delayed firmness decrease, soluble solid content loss, weight loss, yellowing and malonaldehyde accumulation of pepper during storage after pathogen infection.

CONCLUSION

L. farciminis LJLAB1 can be an effective biological control agent to control pepper soft rot caused by Pcb. © 2023 Society of Chemical Industry.

Bacteriocins from lactic acid bacteria and their potential clinical applications

Bacteriocins are ribosomally synthesized antimicrobial peptides that have long been used in the food industry. Being a highly diverse and heterogeneous group of molecules the classification is ever-evolving. Their production is widespread among bacteria; nevertheless, their biosynthesis and mode of action remain fairly similar. With the advances in drug resistance mechanisms, it is important to look for alternatives to conventional approaches. Therefore, the advantages of bacteriocin over antibiotics need to be considered to provide a scientific basis for their use. Particularly in the last decade, intensive studies look at their potential as next-generation therapeutics against drug-resistant bacteria. Bacteriocins from lactic acid bacteria are being tested as controlling agents for bacterial and viral infections; they can inhibit biofilm synthesis and have potential as contraceptives. Bioengineered peptides have shown enhanced activity and thereby indicate the lack of knowledge we possess regarding these bacteriocins. In this review, we have listed various Gram-positive LAB bacteriocins with their synthesis and mechanism of action. Recent developments in screening and purification technologies have been analyzed with an emphasis on their potential clinical applications. Although extensive research has been done to identify multifunctional bacteriocins, it is important to focus on the mechanism of action of these peptides to get them from bench to bedside.

Biodegradation of used polyethylene bags by a new marine strain of Alcaligenes faecalis LNDR-1

Disposable plastic bags of two different chemical compositions and colors were remediated by the application of novel mesophilic group of bacteria isolated from the banks of sea water, using a 10 week soil burial method. The new strain, LNDR-1, was identified as Alcaligens faecalis by its morphological features and 16S rRNA sequencing. LNDR-1 was able to produce extracellular enzymes such as lipase, CMCase, xylanase, and protease, having PET surface degrading activity. It was found that LNDR-1 had a better decay rate of 15.25 ± 1% and 21.72 ± 2.1% for black and white plastic bags respectively in 10 weeks without prior oxidation as compared to S. marcescens. Polyethylene degradation was confirmed by substantial weight loss, alterations in surface topology, and hydrophobicity index and was found to be directly proportional to the ability to form biofilm on the plastic surface. FTIR results suggest presence of different metabolites in the bags treated with bacterial biofilm in comparison to the control setup inferring various types of metabolic pathways. Present study also reveals the ability of the strain to utilize the used polyethylene bag as the carbon source, without any prior treatment, and as per the literature survey, the working strain is with the capacity to biodegrade plastic at a considerably appreciable rate. This study suggests effectual method for the mechanism of biodegradation of plastic mediated by extracellular enzymes and formation of biofilm.