Evaluation of the ability to metabolize 1, 2-propanediol by heterofermentative bacteria of the genus Lactobacillus

Background: New directions of research on lactic acid bacteria include investigation of metabolic pathways for the synthesis and/or metabolism of 1,2-propanediol, commonly used in the food and chemical industry, medicine, pharmacy and cosmetology as well as agriculture. The objective of this study was to compare the capacity of strains representing three diverse heterofermentative species belonging to the genus Lactobacillus to synthesize and/or transform 1,2-PD as well as to suggest new directions of research aimed at commercial use of this metabolite. Results: The novel strain of Lactobacillus buchneri A KKP 2047p, characterized as exhibiting an unusual trait for that species in the form of capacity to metabolize 1,2-PD, grew poorly in a medium containing 1,2-PD as a sole carbon source. The supplementation with glucose facilitated rapid growth of bacteria and use of 1,2-PD for the synthesis of propionic acid. A similar observation was noted for Lactobacillus reuteri. On the other hand, Lactobacillus diolivorans effectively metabolized 1,2-PD which was the sole carbon source in the medium, and the addition of glucose inhibited the synthesis of propionic acid. The experiments also investigated the effect of cobalamin as a diol dehydratase coenzyme involved in the propionic acid synthesis from 1,2-PD whose addition promoted the yield of the reaction in the case of all tested strains. Conclusions: All tested isolates showed the ability to effectively metabolize 1,2-PD (in the presence of cobalamin) and its conversion to propionic acid, which reveals that investigated bacteria meet the essential requirements of microorganisms with a potential application.

Morphological characteristics of maize plants in estimate the silage chemical composition / Características morfológicas de plantas de milho estimam a composição bromatológica da silagem

The aim of this study was to estimate the chemical composition of maize silage based on the morphological characteristics of maize plants and to evaluate the effect of nitrogen fertilization and the inclusion of a microbial inoculant during the ensiling process on the production of maize silage and its morphological, qualitative and fermentative characteristics. The experimental treatments consisted of four levels of nitrogen fertilization with urea (0, 100, 200 and 300 kg ha-1) and the inclusion or exclusion of the microbial inoculants during the ensiling process. A completely randomized design was used in a 4 × 2 factorial arrangement of treatments. The maize silage chemical composition was estimated by evaluating the plant height (PH) and ear characteristics (NRE= number of rows per ear; NKE= number of kernels per ear; ELS= ear length with straw; EL= ear length without straw) using the following equations:CP= -12.44 + 5.871 × PH + 0.01814 × NRE² (R²= 0.89; P < 0.0001); NDF= 587.93-0.78×NKE-11.67×ELS-0.47×EL+0.0000007×NKE³+0.006× EL³ (R²=0.92; P = 0.003); ADF= 41.48 -0.046 × NRE2 (R2 = 0.42; P = 0.02);TDN= 57.81 - 0.0319 × NRE2 (R2 = 0.42; P = 0.02);EDDM= 56.58 + 0.035 × NRE2 (R2 = 0.42; P = 0.02) andNEL= 1.31 + 0.000757 × NRE2 (R2 = 0.41; P = 0.02). In conclusion, nitrogen fertilization increases the silage energy and protein content; while the inclusion of microbial inoculants during the ensiling process does not alter the chemical and fermentative characteristics of the maize silage.

O objetivo do presente estudo foi estimar a composição bromatológica da silagem por meio de características morfoló- gicas das plantas de milho, e avaliar o efeito de níveis de adubação nitrogenada e da inclusão de inoculante microbiano na ensilagem sobre as características produtivas, morfológicas, bromatológicas e fermentativas de silagem de milho. Os tratamentos consistiram em quatro níveis de adubações com ureia: 0; 100; 200 e 300 Kg ha-1, e da inclusão ou não de inoculante microbiano. Foi utilizado um delineamento inteiramente casualizado, com arranjo fatorial de tratamentos 4 × 2. A composição bromatológica da silagem foi estimada pela altura das plantas (AP) de milho e pelas características da espiga (NLE = número de linhas de grãos por espiga; NGE = Número de grãos por espiga; CCP = comprimento da espiga com palha; CSP = comprimento da espiga sem palha) por meio das seguintes equações: PB = -12,44 + 5,871 × AP + 0,01814 × NLE² (R² = 0,89; P < 0,0001); FDN = 587,93 – 0,78 × NGE – 11,67 × CCP – 0,47 × CSP + 0,0000007 × NGE³ + 0,006 × CCP³ (R² = 0,92; P = 0,003); FDA = 41,48 - 0,046 × NLE2 (R2 = 0,42; P = 0,02); NDT = 57,81 – 0,0319 × NLE2 (R2 = 0,42; P = 0,02); DMSE = 56,58 + 0,035 × NLE2 (R2 = 0,42; P = 0,02) e ELL = 1,31 + 0,000757 × NLE2 (R2 = 0,41; P = 0,02). Pode-se concluir que a adubação nitrogenada aumenta o teor de energia e de proteína da silagem; enquanto a inclusão de inoculante microbiano não altera as características bromatológicas e fermentativas da silagem de milho.