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This study reports the characterization of the Tetrasphaera duodecadis bacteria and the techniques used therein. In order to evaluate the morphological characteristics of the T. duodecadis bacteria scanning electron microscope (SEM) was used throughout its different growth stages. These microorganisms were grown in vitamin B12 broths with 1% tryptone, 0.2% yeast extract, and 0.1% glucose. The turbidimetric method was employed for the determination of bacterial concentration and growth curve. The SEM results show small agglomerates of 0.8 ± 0.05 µm during the lag phase, and rod-like shapes during the exponential phase with similar shapes in the stationary phase.

In this study we describe a sensitive amperometric microbial biosensor that is fast, economic, reliable, and can compete with the existing proposed methods for vitamin B12 determination. Taking advantage of the bacterial strain Tetrasphaera duodecadis which oxidizes Vitamin B12 with oxygen consumption, we shaped a promising alternative tool for the direct and specific determination of vitamin B12 in different samples without pre-treatment. For this purpose, a Vitamin B12Amperometric microbial biosensor was constructed based on one-step immobilization of the bacterium by filtration of a concentrated bacterial mass through a 0.15 μm pore size cellulose filter and fixed on a Clark-type oxygen probe, serving as a transducer, and exploiting the described processes. The results obtained indicate a sensitive capability with a linear sensor concentration range from 10 -7 molL -1 to 10 -5 molL -1 and the response time about 700 seconds at 10 -6 molL -1 . Furthermore, the Tetrasphaera duodecadis membrane attached to the Clark type oxygen probe has an estimated 1-month lifetime at room temperature. In addition, the developed prototype allowed the assessment of B12 status directly in samples prepared for that purpose. The results were well correlated with those obtained with commercial samples, thus demonstrating that the proposed microbial sensor offers an accurate and useful analytical tool that can be easily applied to prevent diseases caused by the lack of vitamin B12.

The increasing amounts of residual cellulose films generated as wastes all over the world represent a big scale problem for the meat industry regarding to environmental and economic issues. The use of residual cellulose films as a feedstock of glucose-containing solutions by acid hydrolysis and further fermentation into lactic acid and biosurfactants was evaluated as a method to diminish and revalorize these wastes. Under a treatment consisting in sulfuric acid 6% (v/v); reaction time 2 h; solid liquid ratio 9 g of film/100 mL of acid solution, and temperature 130 °C, 35 g/L of glucose and 49% of solubilized film was obtained. From five lactic acid strains, Lactobacillus plantarum was the most suitable for metabolizing the glucose generated. The process was scaled up under optimized conditions in a 2-L bioreactor, producing 3.4 g/L of biomass, 18 g/L of lactic acid, and 15 units of surface tension reduction of a buffer phosphate solution. Around 50% of the cellulose was degraded by the treatment applied, and the liqueurs generated were useful for an efficient production of lactic acid and biosurfactants using L. plantarum. Lactobacillus bacteria can efficiently utilize glucose from cellulose films hydrolysis without the need of clarification of the liqueurs.

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