Influence of different milk-coating enzymes on the process of producing soft cheeses

The effect of the type of milk clotting enzyme (MCE) on the duration of milk coagulation, parameters of the composition of whey and cheeses, and the output of cheeses in the production of soft cheese such as “Lyubitel'skiy” were investigated. Three brands of MCE of different origins were investigated: Marzyme® (MCE of microbial origin based on Rhizomucor miehei protease), Naturen® (calf rennet) and Chy-max® M (recombinant camel chymosin). It was established that MCEs had different ratios of milk clotting activity (MCA) to total proteolytic activity (PA). It was determined that the MCA/PA ratio, which characterizes the degree of specificity of the MCE action with regard to kappa-casein, in Chy-max M 1000 is ~7 times higher than that of Naturen and ~50 times higher than that of Marzyme. Such differences did not lead to a negative effect when using the Marzyme preparation in the production of soft cheeses. There were no statistically significant differences in the amount of dry matter loss of the curd into the whey, physicochemical parameters and output between the variants of cheeses made with the studied brands of MCE. Shorter duration of milk clotting (16.5 min) was observed with Marzyme than with MCE of Naturen (20.5 min) and Chy-max M (22.5 min). The results of the coagulation duration were explained by the stimulation of the activity of MCE of microbial origin, by the pH level of milk before coagulation (below pH 6.4). It was shown that modern MCEs of microbial origin could be recommended as a cost-effective replacement for more expensive rennet and recombinant chymosins in the production of soft and fresh cheeses.

Effect of Geobacillus toebii GT-02 addition on composition transformations and microbial community during thermophilic fermentation of bean dregs

Bean dregs can be prepared into organic fertilizer by microbial fermentation. Geobacillus toebii GT-02, which has promoting effect on bean dregs fermentation, was isolated from horse dung and it grows within a range of 40–75 °C and pH 6.50–9.50. The effectiveness of GT-02 addition on composition transformations and the microbial community in bean dregs thermophilic fermentation at 70 °C for 5 days was investigated (T1). Fermentation of bean dregs without GT-02 served as control (CK). The results showed that T1 (the germination index (GI) = 95.06%) and CK (GI = 86.42%) reached maturity (defined by GI ≥ 85%) on day 3 and day 5, respectively. In addition, the total nitrogen loss of T1 (18.46%) on day 3 was lower than that in CK (24.12%). After thermophilic fermentation, the total organic carbon and dry matter loss of T1 (53.51% and 54.16%) was higher than that in CK (41.72% and 42.82%). The mean microbial number in T1 was 4.94 × 107 CFUs/g dry matter, which was 5.37 times higher than that in CK. 16S rDNA sequencing identified Bacillus, Geobacillus and Thermobacillus as dominant in CK, while Bacillus, Ammoniibacillus and Geobacillus were dominant in T1. A canonical correspondence analysis showed that Geobacillus and Ammoniibacillus were positively correlated with the GI. Thus, thermophilic fermentation with GT-02 can promote the maturity of bean dregs, which indicated the potential application value of GT-02 in thermophilic fermentation.

Effects of N Fertilization During Cultivation and Lactobacillus plantarum Inoculation at Ensiling on Chemical Composition and Bacterial Community of Mulberry Silage

As unconventional forage source, mulberry (Morus alba L.) has been cultivated to alleviate animal feed shortages. This study aimed to investigate the effects of N fertilization during cultivation and Lactobacillus plantarum inoculation at ensiling on the chemical composition and bacterial community of mulberry silage. Mulberry was separately cultivated under two N fertilization rates (N1, 390 kg/ha/year; N2, 485 kg/ha/year) in 2016–2019, harvested on 30 April (the first-cut) and 15 June (the second-cut) in 2019, and then chopped for producing small bag silage. The silage was treated without (control) or with L. plantarum (LP, a recommended application rate of 105 cfu/g on fresh matter basis). After storage of 60 days in dark room at ambient temperature, silage was sampled for analysis of chemical and microbial compositions. Higher (P < 0.05) final pH value and acetic acid content and lower (P < 0.05) lactic acid content were found in silage of mulberry under N2 fertilization, resulting in more dry matter loss than that under N1 fertilization. Compared with control, inoculation of LP at ensiling increased (P < 0.05) lactic acid content and decreased (P < 0.05) final pH value, acetic acid and propionic acid contents of silage, by advancing the dominance of Lactobacillus and reducing the abundance of Enterococcus and Enterobacter. In particular, inoculation of LP at ensiling decreased (P < 0.05) dry matter loss and butyric acid content of first-cut silage. In conclusion, inoculation of LP at ensiling could reduce the undesirable effects from high N fertilization rate during cultivation on silage quality of mulberry harvested at different growing seasons.

Obtaining Cellulose-Available Raw Materials by Pretreatment of Common Agro-Forestry Residues With Pleurotus spp.

The goals of the present study were to characterize the profile of ligninolytic enzymes in five Pleurotus species and determine their ability to delignify eight common agro-forestry residues. Generally, corn stalks were the optimal inducer of Mn-dependent peroxidase activity, but the activity peak was noted after wheat straw fermentation by P. eryngii (3066.92 U/L). P. florida was the best producer of versatile peroxidase, especially on wheat straw (3028.41 U/L), while apple sawdust induced the highest level of laccase activity in P. ostreatus (49601.82 U/L). Efficiency of the studied enzymes was expressed in terms of substrate dry matter loss, which was more substrate-than species-dependent. Reduction of substrate dry mass ranged between 24.83% in wheat straw and 8.83% in plum sawdust as a result of fermentation with P. florida and P. pulmonarius, respectively. The extent of delignification of the studied substrates was different, ranging from 51.97% after wheat straw fermentation by P. pulmonarius to 4.18% in grapevine sawdust fermented by P. ostreatus. P. pulmonarius was also characterized by the highest cellulose enrichment (6.54) and P. ostreatus by very low one (1.55). The tested biomass is a highly abundant but underutilized source of numerous value-added products, and a cocktail of ligninolytic enzymes of Pleurotus spp. could be useful for its environmentally and economically friendly transformation.

AGRO-FORESTRY RESIDUES VALORIZATION BY LIGNINOSOME OF GRIFOLA FRONDOSA

Grifola frondosa HAI 1232 was tested for ligninolytic enzyme activities and for lignin, cellulose and hemicellulose degradation during cultivation on eight common agro-forestry residues in Serbia. Wheat straw was favorable lignocellulosic for the production of Mn-dependent and Mn-independent peroxidases (2513.89 and 354.17 U L-1, respectively), while selected residues inhibited the synthesis of laccases. The highest lignin removal was observed during fermentation of blackberry sawdust (36.75%), while the highest selectivity index was recorded on oak sawdust (4.34). The dry matter loss varied between 8.17% in corn stalks and 14.16% in apple sawdust. According to the presented results, it can be concluded that G. frondosa HAI 1232 could be an important participant in various biotechnological processesdue to its high capacity to selectively degrade different agro-forestry residues.

Effects of Vanillic Acid on Dynamic Fermentation Parameter, Nitrogen Distribution, Bacterial Community, and Enzymatic Hydrolysis of Stylo Silage

Vanillic acid (VA) is a phenolic acid derivative commonly found in plants and foods, with a pleasant creamy odor and pharmacologic activities, which is hypothesized to help improve silage fermentation. The silage profile of stylo silage ensiled with addition of VA was evaluated. The results showed that VA addition resulted in the decrease of pH value (5.22 vs. 4.33), dry matter loss (5.37 vs. 2.51% DM), and ammonia-N proportion (14.57 vs. 1.51% CP) of stylo silage as well as the increase of lactic acid concentration (0.51 vs. 1.17% DM), true protein proportion (51.18 vs. 58.47% CP), and saccharification yield (113.64 vs. 126.40 mg/g DM). Meanwhile, bacterial community of stylo silage was altered, where the relative abundance of Enterobacter, Clostridium, and Kosakonia decreased and that of Commensalibacter and Methylobacterium increased. In conclusion, it is suggested that VA could be used as a novel silage additive to improve silage fermentation and nutrient preservation of stylo silage.

Study on the Rehydration Quality Improvement of shiitake Mushroom by Combined Drying Methods

The aim of study is to improve the rehydration quality of dried shiitake mushrooms for their instant food manufacturers and fast restaurants. Serial combined drying methods were investigated to achieve this objective: either instant controlled pressure drop drying (DIC) or freeze drying (FD) was used as the treatments for microstructure improvement, and they were applied either before or after an additional drying step at low (35 °C) or high (65 °C) temperatures. Dried mushrooms were assessed for quality indicators like relative volume, rehydration rate, dry matter loss and sensory scores. Microstructure properties were inferred to understand the physical mechanisms of quality changes. Principal component analysis (PCA) was used to cluster treatments and to identify combinations of drying techniques, rendering improved quality. Consequently, it was shown that DIC treatment before hot air drying at 35 °C was shown to be the most promising combined drying method to enhance the rehydration quality, leading to a high volume recovery ratio, low dry matter loss after rehydration, and high rehydration rates. This good performance could be explained by the retention of pore interconnectivity resulting from the slight expansion of porous structure during DIC and the retention of cell membrane integrity.

Effect of Geobacillus toebii addition on composition transformations and microbial community in thermophilic bean dreg composting

A thermophilic bacterium, Geobacillus toebii GT-02, was successfully isolated from horse dung. The effectiveness of Geobacillus toebii GT-02 addition on composition transformations and the microbial community in bean dreg composting at 70°C for 5 days was investigated (T1), and the control consisted of bean dreg compost without GT-02 (CK). After 5 days, T1 presented higher total nitrogen contents (2.77%) and lower carbon-to-nitrogen ratios (14.4) than CK (2.34% and 16.9, respectively). The germination index (GI) of T1 was 135%, which was 56% higher than that of CK (86%). The dry matter loss in T1 was 54.16% (26.82% higher than the CK value (42.82%)). The mean microbial number in T1 was 4.94x107 CFUs/g dry matter, which was 5.37 times that in CK. 16S rDNA sequencing identified Bacillus, Geobacillus and Thermobacillus as dominant in CK, while Bacillus, Ammoniibacillus and Geobacillus were dominant in T1. A canonical correspondence analysis showed that Geobacillus and Ammoniibacillus were positively correlated with the GI. Thus, composting with GT-02 can promote the maturity of bean dregs, and GT-02 has potential commercial application in thermophilic composting.

Effects of Splits Content on Dry Matter Loss Rates of Soybeans Measured Using a Static Grain Respiration Measurement System

HighlightsRespiration rate increased with the percentage of split soy beans.The splits multiplier for soybeans appears to be more sensitive than the corn damage multiplier.The relationship between the split percentage and splits multiplier for soybeans is approximately linear.A value for the splits multiplier is provided for 18% moisture content soybeans stored at 35°C.Abstract. The objectives of this study were to compare the effects of 0% to 16% (w/w) splits content (xs) of soybeans stored at 35°C and 18% moisture content (w.b.) on dry matter loss rates (vDML) and to determine a splits multiplier (MS) for soybeans stored at these conditions, similar to the damage multiplier (MD) used in ASABE Standard D535 for shelled corn. Effects of percentage by weight splits (xs) on MS and safe storage time are expected to be greater than MD for corn because soybeans are prone to cracking and splitting, lipid oxidation, and protein degradation, all of which lead to grain dry matter and quality losses. Results indicated that vDML increased with increasing xs, and the mean vDML was 1.5 times greater for samples with 16% splits than for samples with 4% splits. The MS for soybeans was linearly correlated with xs, decreasing from 1.0 to 0.60 for 0% to 16% splits, respectively. Soybeans appeared to be more sensitive to percent by weight splits than corn was to the presence of damaged kernels. In Standard D535, the MD for corn only decreased from 1.0 to 0.8 when percent (w/w) damaged kernel content increased from 30% to 40%. In comparison, it should be noted that damage to soybeans was defined differently from damage to corn. This research is useful in defining MS for 18% moisture content soybeans stored at 35°C under hermetic conditions. The procedures outlined in this article may be used in the future to more formally define a soybean MS that covers a wider range of moisture contents, storage conditions, and possibly an MD based on other factors included in the USDA definitions of damaged soybean kernels. Keywords: Allowable storage time, Grain quality, Splits multiplier.