Effects of Proteolytic and Lipolytic Enzyme Supplementations on Lipolysis and Proteolysis Characteristics of White Cheeses

Biological modification and industrial applications of microbial lipases: A general review

With the rapid development of industrialization and modern science, lipase has garnered pervasive attention. Lipases (EC 3.1.1.3) are enzymes exhibiting strong substrate specificity, high stereoselectivity, and solvent stability, which renders them a crucial biocatalyst. However, natural lipases often cannot meet the requirements of application and research in terms of activity, enantioselectivity, or thermal stability. With the continuous advancement of genetic engineering and protein engineering technologies, exploring efficient enzyme molecular modification techniques is a major task of enzyme engineering. We here review the current research status and progress of molecular modification techniques for lipases, including directed evolution, rational design, semi-rational design, and immobilization. Additionally, this article analyses lipase application prospects in food processing, environment, medical and pharmaceutical, cosmetics, and other fields. This article provides comprehensive information for the molecular modification and application research of lipases and contributes to providing reference for researchers in relevant fields.

Enhancing the microbial dynamics, volatile profile, and ripening efficiency of white brined cheese using Lactiplantibacillus plantarum L33 as a probiotic co-culture

Lactiplantibacillus plantarum L33 was used as a co-culture in the production of white brined cheese. The study compared control samples (without co-culture) and those including the co-culture at 1, 15 and 30 days of ripening, assessing various factors such as pH, moisture content, protein and fat levels, proteolysis intensity, organic acids, aromatic compounds, bacterial dynamics, hardness, and sensory evaluations. The results indicated that the cheese samples containing Lpb. plantarum L33 exhibited a higher moisture content (15 %) and lower hardness (11 %) compared to the control sample, while fat and protein levels remained consistent across both samples. Moreover, the co-culture sample had higher levels of lactic acid, acetic acid, and aromatic compounds such as acetone and diacetyl. Analysis of bacterial dynamics revealed that the presence of co-culture and storage time significantly enhanced the relative abundance of bacteria in the samples containing the co-culture, with the highest relative abundance found for Streptococcus salivarius subsp. thermophilus (107.27), followed by Lpb. plantarum L33 (25.51), Lactococcus lactis subsp. lactis (7.46), and Lactococcus lactis subsp. cremoris (0.74). The co-culture sample also received favorable sensory scores for overall acceptance. The findings suggest that a strain with moderate proteolytic activity can effectively reduce the ripening time of cheese by enhancing proteolysis intensity, thereby accelerating the production of aromatic compounds.

Evaluation of the biofilm-forming ability and molecular characterization of dairy Bacillus spp. isolates

Food processing lines represents a suitable environment for bacterial biofilm formation. One of the most common biofilm-forming genera in dairy processing plants is Bacillus, which includes species that may have a negative impact on safety and/or quality of dairy products. In the current study, we evaluated the biofilm forming ability and molecular characteristics of dairy Bacillus spp. isolates (B. cereus and B. subtilis). Reference strains (B. cereus ATCC 14579 and B. subtilis NCTC 3610) were also included in the experiment. All isolates were screened by micro-titer plate (96 wells) to assess their ability to form biofilm. Then, they were tested on two common food contact surfaces (polystyrene and stainless steel) by using 6-well plates and AISI 316 stainless steel coupons. Biofilm formation, expressed as biofilm production index (BPI), was higher on polystyrene than stainless steel (except for B. cereus ATCC 14579). These observations were further confirmed by scanning electron microscopy, which allowed the microscopy observation of biofilm structure. Moreover, a possible correlation among total viable cell counts (CFU) and BPI was examined, as well as a connection among biofilm formation and bacterial cell hydrophobicity. Finally, whole genome sequencing was performed highlighting a genetic similarity among the strains belonging to the same species. The presence of selected genes involved in biofilm formation was also examined showing that strains with a greater presence of these genes were able to produce more biofilm in the tested materials. Additionally, for B. cereus strains enterotoxin genes were detected.

Effect of Fermented Meat and Bone Meal–Soybean Meal Product on Growth Performance in Broilers

In this study, we screen the proteolytic activity of Bacillus species in meat and bone meal (MBM) and investigate the effects of fermented MBM–soybean meal products (FMSMPs) on the growth performance of broilers. In Trial 1, FMSMPs were fermented using four strains—Bacillus siamensis M3 (M3), B. velezensis M5 (M5), B. subtilis M6 (M6), and B. subtilis M20 (M20)—all of which presented more total peptides and higher degrees of hydrolysis (DH) than Bacillus subtilis var. natto N21 (N21). In Trial 2, 280 0-day-old Arbor Acres broilers, with equal numbers of both sexes, were randomly assigned into 5% fish meal (FM), MBM–soybean meal (MSM, as control), and N21, M3, M5, M6, and M20 FMSMP groups. The results demonstrated that the crude protein, total amino acids, alkaline protease, trichloroacetic acid–soluble nitrogen (TCA-SN), TCA-SN/total nitrogen, total peptides, DH, and free-hydroxyproline levels in the M6 group were greater than those in any other group (p < 0.05). Furthermore, the weight gain in the M6 group was superior to that of the FM and MSM groups in 0–21 and 0–35-day-old broilers (p < 0.05). In conclusion, B. subtilis M6 likely efficiently decomposes MSM to improve the protein properties and nutritional value of the product after fermentation. Supplementation with 5% FMSMP may promote weight gain in broilers.

Changes in Key Aroma Compounds and Esterase Activity of Monascus-Fermented Cheese across a 30-Day Ripening Period

Monascus-fermented cheese (MC) is a new type of mold-ripened cheese that combines a traditional Chinese fermentation fungus, Monascus purpureus M1, with Western cheese fermentation techniques. In this study, the compositions of the volatile aroma compounds in MC were analyzed during a 30-day ripening period using SPME-Arrow and GC-O-MS. The activity of esterase in MC, which is a key enzyme catalyzing esterification reaction, was determined and compared with the control group (CC). Next, sensory analysis was conducted via quantitative descriptive analysis followed by Pearson correlation analysis between esterase activity and the key flavor compounds. A total of 76 compounds were detected. Thirty-three of these compounds could be smelled at the sniffing port and were identified as the key aroma compounds. The esterase activity in MC was found to be 1.24~1.33 times that of the CC. Moreover, the key odor features of ripened MC were alcohol and fruity flavors, considerably deviating from the sour and cheesy features found for the ripened CC. Furthermore, correlation analysis showed that esterase activity was strongly correlated (|r|> 0.75, p < 0.05) with various acids such as pentanoic and nonanoic acids and several aromatic esters, namely, octanoic acid ethyl ester and decanoic acid ethyl ester, revealing the key role that esterases play in developing the typical aroma of ripened MC.

Microencapsulation of a Commercial Food-Grade Protease by Spray Drying in Cross-Linked Chitosan Particles

In this study, the use of spray-drying technology for encapsulating Flavourzyme® (protease–peptidase complex) was evaluated to overcome the limitations (low encapsulation efficiency and no large-scale production) of other encapsulation processes. To the best of our knowledge, spray drying has not been applied previously for the immobilization of this enzyme. Firstly, bovine serum albumin (BSA), as a model protein, was encapsulated by spray drying in chitosan and tripolyphoshate (TPP) cross-linked-chitosan shell matrices. The results showed that the chitosan–TPP microcapsules provided a high encapsulation efficiency and better protein stability compared to the non-crosslinked chitosan microcapsules. The effect of enzyme concentration and drying temperature were tested during the spray drying of Flavourzyme®. In this regard, an activity yield of 88.0% and encapsulation efficiency of 78.6% were obtained with a concentration of 0.1% (v/v) and an inlet temperature of 130 °C. Flavourzyme®-loaded chitosan microcapsules were also characterized in terms of their size and morphology using scanning electron microscopy and laser diffractometry.

Characterization of Vegetative Bacillus cereus and Bacillus subtilis Strains Isolated from Processed Cheese Products in an Italian Dairy Plant

Processed cheese is a commercial product characterized by high microbiological stability and extended shelf life obtained through the application of severe heat treatment. However, spore-forming bacteria can survive through thermal processes. Among them, microorganisms belonging to Bacillus genus have been reported. In this study, we examined the microbiological population of the first hours' production of processed cheeses in an Italian dairy plant during two seasons, between June and October 2020. Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) was used to identify bacteria colonies, allowing the isolation of Bacillus cereus and Bacillussubtilis strains. These results were further confirmed by amplification and sequencing of 16 rRNA bacterial region. A multi-locus sequence type (MLST) analysis was performed to assess the genetic similarity among a selection of isolates. The fourteen B. cereus strains showed two sequence types: ST-32 was observed in only one strain and the ST-371 in the remaining thirteen isolates. On the contrary, all twenty-one B. subtlis strains, included in the study, showed a new allelic profile for the pycA gene, resulting in a new sequence type: ST-249. For B. cereus strains, analysis of toxin genes was performed. All isolates were positive for nheABC, entFM, and cytK, while hblABCD, bceT, and ces were not detected. Moreover, the biofilm-forming ability of B. cereus and B. subtilis strains was assessed, and all selected isolates proved to be biofilm formers (most of them were stronger producers). Considering the genetical similarity between isolates, jointly with the capacity to produce biofilm, the presence of a recurring Bacillus population could be hypothesized.

Optimizing the acceleration of Cheddar cheese ripening using response surface methodology by microbial protease without altering its quality features

Cheddar cheese proteolysis were accelerated employing Penicillium candidum PCA1/TT031 protease into cheese curd. In the present study, several of the significant factors such as protease purification factor (PF), protease concentration and ripening time were optimized via the response surface methodology (RSM). The ideal accelerated Cheddar cheese environment consisted of 3.12 PF, 0.01% (v/v) protease concentration and 0.6/3 months ripening time at 10 °C. The RSM models was verified to be the most proper methodology for the maintain of chosen Cheddar cheese. Under this experimental environment, the pH, acid degree value (ADV), moisture, water activity (a_w), soluble nitrogen (SN)%, fat and overall acceptability were found to be 5.4, 6.6, 35%, 0.9348, 18.8%, 34% and 13.6, respectively of ideal Cheddar cheese. Furthermore, the predicted and experimental results were in significant agreement, which confirmed the validity and reliability of the suggested method. In spite of the difference between the ideal and commercial Cheddar cheese in the concentration of some of amino acids and free fatty acids, the sensory evaluation did not show any significant difference in aroma profile between them.

Determination of changes in the microbial and chemical composition of Țaga cheese during maturation

Țaga cheese is a traditional Romanian smear-ripened cheese made from bovine milk and identified with the name of the village and caves where it is produced. As no previously reported microbiological and chemical studies have been undertaken on this product, this research aimed to investigate the microbiological and biochemical characteristics which ensure the uniqueness of Țaga cheese during the ripening process, to inform producers as to key quality determinants. Cheese samples, consisting of retail blocks, were collected on days 2, 5, 12, 18, and 25 of the ripening process. The evolution of lactic microbiota during the production and maturation of traditional cheeses involves isolating lactic acid microorganisms present in cheese. Cheese samples were analyzed for pH, fat, NaCl, fatty acids, and volatile compounds. The microbial ecosystem naturally changes during the maturation process, leading to variation in the microorganisms involved during ripening. Our results show that specific bacteria were identified in high levels during the entire ripening process and may be responsible for milk fat lipolysis contributing directly to cheese flavor by imparting detailed fatty acid flavor notes, or indirectly as precursors formation of other flavor compounds.

Total nitrogen, water-soluble nitrogen and free amino acids profile during ripening of soft cheese enriched with Nigella sativa seed oil

Various antimicrobial solutions have been tested as additives for raw milk traditional cheeses, among which Nigella sativa cold pressed seed oil (NSSO) is recognized for its positive effect on the microbial quality of such products. The overall effect on the quality of enriched cheeses during ripening is still under extensive investigation. Three batches of traditional raw milk brined cheese were included in the current experiment: control cheese without Nigella sativa seed oil (NSSO) and cheese samples enriched with 0.2 and 1% w/w NSSO. Experimental cheese samples were analyzed in duplicates for total nitrogen content (TN), at 0, 14, 28 and 42 days of ripening, while single determinations of total nitrogen (WSN) and free amino acids (FAA) were performed at 14, 28 and 42 ripening days. The TN content revealed similar values for control cheeses and NSSO cheeses, and no significant differences were noticed within the three treatment groups (p >.05) throughout ripening. WSN values followed a significant rising shift in all cheeses during ripening, yet computing data obtained for the three considered treatments, despite an obvious higher WSN content of NSSO enriched cheeses, no statistical significance could be associated to this difference. The FAA composition of the experimental cheeses, varied quantitatively, by increasing with ripening time, but no qualitative variation was noticed during the follow-up period. The FAA composition of the did not vary significantly within treatments.