Lactobacillus casei expressing methylglyoxal synthase causes browning and heterocyclic amine formation in Parmesan cheese extract

Abstract

Undesired browning of Parmesan cheese can occur during the latter period of ripening and cold storage despite the relative absence of reducing sugars and high temperatures typically associated with Maillard browning. Highly reactive α-dicarbonyls such as methylglyoxal (MG) are products and accelerants of Maillard browning chemistry and can result from the microbial metabolism of sugars and AA by lactic acid bacteria. We demonstrate the effects of microbially produced MG in a model Parmesan cheese extract using a strain of Lactobacillus casei 12A engineered for inducible overexpression of MG synthase (mgsA) from Thermoanaerobacterium thermosaccharolyticum HG-8. Maximum induction of plasmid-born mgsA led to 1.6 mM MG formation in Parmesan cheese extract and its distinct discoloration. The accumulation of heterocyclic amines including β-carboline derivatives arising from mgsA expression were determined by mass spectrometry. Potential MG-contributing reaction mechanisms for the formation of heterocyclic amines are proposed. These findings implicate nonstarter lactic acid bacteria may cause browning and influence nutritional aspects of Parmesan by enzymatic conversion of triosephosphates to MG. Moreover, these findings indicate that the microbial production of MG can lead to the formation of late-stage Maillard reaction products such as melanoidin and β-carbolines, effectively circumventing the thermal requirement of the early-and intermediatestage Maillard reaction. Therefore, the identification and control of offending microbiota may prevent latestage browning of Parmesan. The gene mgsA may serve as a genetic biomarker for cheeses with a propensity to undergo MG-mediated browning.Accurate mass was determined by liquid chromatography (LC) electrospray ionization time-of-flight (Agilent 1969A, Agilent Technologies, Santa Clara, CA). The mass to charge ratio (m/z) of fragment ions and their relative intensity were generated using a collision energy of 40 eV and determined by LC-MS/MS (Sciex QTRAP 5500, Sciex, Framingham, MA). Figure 3. Liquid chromatography tandem mass spectrometry (LC-MS/MS) comparison between β-carboline derivatives formed in Parmesan cheese extract (PCE) from Lactobacillus casei 12A expressing methylglyoxal synthase (mgsA) and 1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid (THβCA) and Harman. (A) Compound 4 and THβCA, and (B) compound 6 and Harman. The mass to charge ratio (m/z) of fragment ions and their relative abundance in samples and commercially available standards were generated using a collision energy of 40 eV and detected by LC-MS/MS (Thermo TSQ Quantum Discovery Max, Thermo Fisher Scientific, Waltham, MA). The co-elution profile of the compound and standard is depicted in the upper right-hand corner of each mass spectrum.

A Novel Organism Lactobacillus wasatchensis: Growth, Detection, Gassing Defects in Cheese, Control Strategy and Future Research Opportunities: A Review

“…wasatchensis. Gandhi et al (2019) in their study reported about Lactobacillus casei expressing methylglyoxal synthase causes browning and heterocyclic amine formation in Parmesan cheese extract, however, to our knowledge similar study on understanding the ability of Lb. wasatchensis to generate methylglyoxal and heterocyclic amine responsible for browning has not been done yet.…”

Unravelling Formaldehyde Metabolism in Bacteria: Road towards Synthetic Methylotrophy

“…The primary atmospheric sources of formaldehyde are either anthropogenic (indoor pollution through building materials, vehicle exhaust gases, various combustion sources, and fugitive industrial emissions) or biogenic (live and decaying plants, biomass burning, and seawater) [2][3][4]. Formaldehyde can also be formed as part of bacterial metabolism in biological processes such as the demethylation of lignins or Strecker degradation of glycine with methylglyoxal [5]. High levels of formaldehyde can hamper cell functions due to its cytotoxic effect, which is provoked by its electrophilic reactivity [6].…”

Identification and characterization of a moonlighting protein-enolase for surface display in Streptococcus thermophilus

“…Lactic acid bacteria (LAB) are widely used in dairy fermented products and pharmaceutical industry owing to their generally regarded as safe (GRAS) status [1]. Moreover, because of their ability to survive in harsh conditions including low pH, the gastro-intestinal tract (GIT) and harsh industrial fermentation processes, LAB have gained more attention to serve as cell factories for delivering bioactive molecules or vaccines to mucosal tissues [2][3][4][5] and production of high-valuable enzymes [6][7][8][9].…”