Effect of Various Strains of Lactobacillus buchneri on the Fermentation Quality and Aerobic Stability of Corn Silage

The aerobic deterioration of silage nutrients is inevitable in tropical countries, causing negative consequences in animal production systems. Aiming to minimize the losses, the effects of Lactobacillus buchneri strains on fermentation profile and aerobic stability of corn silages were evaluated. The experiment was conducted under a completely randomized design with 13 treatments and three replicates. The treatments were noninoculated, commercial L. buchneri (CI), and 11 wild strains of L. buchneri: LB-56.1, LB-56.2, LB-56.4, LB-56.7, LB-56.8, LB-56.9, LB-56.21, LB-56.22, LB-56.25, LB-56.26, and LB-56.27. The treatments could be divided into three different groups according to silage pH and acetic acid concentration. Silages inoculated with LB-56.1, LB-56.4, and LB-56.9 presented higher pH, whereas intermediate values were observed for LB-56.2, LB-56.7, and LB-56.8. The highest acetic acid production was observed for LB-56.1 and LB-56.7. On the other hand, lowest concentrations were found for CI, LB-56.22, LB-56.25, LB-56.26, and LB-56.27. Higher amounts of NH3–N were observed for LB-56.8, LB-56.21, LB-56.22, and LB-56.27 silages than others. Silage inoculation with CI, LB-56.1, LB-56.2, LB-56.4, LB-56.8, LB-56.9, and LB-56.25 strains had higher aerobic stability than others (59.7 vs. 41.2 h). The L. buchneri strains LB-56.1, LB-56.2, LB-56.4, LB-56.8, LB-56.9, and LB-56.25 provided potential features to improve the aerobic stability of corn silage.

Production of R- and S-1,2-propanediol in engineered Lactococcus lactis

Abstract1,2-propanediol (1,2-PDO) is a versatile chemical used in multiple manufacturing processes. To date, some engineered and non-engineered microbes, such as Escherichia coli, Lactobacillus buchneri, and Clostridium thermosaccharolyticum, have been used to produce 1,2-PDO. In this study, we demonstrated the production of R- and S-1,2-PDO using engineered Lactococcus lactis. The L- and D-lactic acid-producing L. lactis strains NZ9000 and AH1 were transformed with the plasmid pNZ8048-ppy harboring pct, pduP, and yahK genes for 1,2-PDO biosynthesis, resulting in L. lactis LL1 and LL2, respectively. These engineered L. lactis produced S- and R-1,2-PDO at concentrations of 0.69 and 0.50 g/L with 94.4 and 78.0% ee optical purities, respectively, from 1% glucose after 72 h of cultivation. Both 1% mannitol and 1% gluconate were added instead of glucose to the culture of L. lactis LL1 to supply NADH and NADPH to the 1,2-PDO production pathway, resulting in 75% enhancement of S-1,2-PDO production. Production of S-1,2-PDO from 5% mannitol and 5% gluconate was demonstrated using L. lactis LL1 with a pH–stat approach. This resulted in S-1,2-PDO production at a concentration of 1.88 g/L after 96 h of cultivation. To our knowledge, this is the first report on the production of R- and S-1,2-PDO using engineered lactic acid bacteria.

Screening of High 1,2-Propanediol Production by Lactobacillus buchneri Strains and Their Effects on Fermentation Characteristics and Aerobic Stability of Whole-Plant Corn Silage

The study was conducted to screen high 1,2-propanediol produced by Lactobacillus buchneri strains, isolated from baled silages stored for 1 or 2 years, and to evaluate their effects on fermentation quality and aerobic stability of whole-plant corn silage. In total, 31 L. buchneri strains were isolated from alfalfa, whole-plant corn and oat silages. Based on growth performance and 1,2-propanediol and acetic acid production, two strains, L. buchneri 9-2 and L. buchneri 10-1, from alfalfa silage, were further assessed in an ensiling trial on whole-plant corn. The corn silage inoculated with L. buchneri 9-2 or L. buchneri 10-1 had a higher concentration of 1,2-propanediol (34.7 or 34.6 g/kg dry matter (DM)) and acetic acid (47.2 or 45.9 g/kg DM) in comparison with L. buchneri 40788 (reference strain) treated silage (19.5 and 35.9 g/kg DM) after 90 d of fermentation. In addition, these two strains performed better in improving silage aerobic stability relative to control and L. buchneri 40788. The results above indicated that L. buchneri 9-2 and L. buchneri 10-1 could be candidate strains to increase 1,2-propanediol and acetic acid concentrations and improve the aerobic stability of whole-plant corn silage.

Silage quality and biogas production from Spartina pectinata L. fermented with a novel xylan-degrading strain of Lactobacillus buchneri M B/00077

The aim of the current study was to determine the ability of the Lactobacillus buchneri M B/00077 strain to degrade xylan, its impact on the quality of silage made from the lignocellulosic biomass of Spartina pectinata L., as well as the efficiency of biogas production. In the model in vitro conditions the L. buchneri M B/00077 strain was able to grow in a medium using xylan as the sole source of carbon, and xylanolytic activity was detected in the post-culture medium. In the L. buchneri M B/00077 genome, genes encoding endo-1,4-xylanase and β-xylosidase were identified. The silages prepared using L. buchneri M B/00077 were characterized by a higher concentration of acetic and propionic acids compared to the controls or the silages prepared with the addition of commercial xylanase. The addition of bacteria increased the efficiency of biogas production. From the silages treated with L. buchneri M B/00077, 10% and 20% more biogas was obtained than from the controls and the silages treated with commercial xylanase, respectively. The results of the current study indicated the strain L. buchneri M B/00077 as being a promising candidate for further application in the field of pretreatment of lignocellulosic biomass.