Modelado de la biodegradación en biorreactores de lodos de hidrocarburos totales del petróleo intemperizados en suelos y sedimentos (Biodegradation modeling of sludge bioreactors of total petroleum hydrocarbons weathering in soil and sediments)

Avocado (Persea americana Mill) seeds, a rich source of starch and micronutrients, are a major waste product from the agroindustrial processing of avocados. Here we designed and developed an experimental culture medium (ECM) from hydrolysed avocado seeds, supplemented with M9 salts (10% v/v). Breaking of starch granules of avocado seeds due to hydrolysis treatments was analysed by morphology and morphometry of granules. We evaluated the ECM functionality by measuring the growth of Escherichia coli as affected by (i) the carbon source (reducing sugars concentration), (ii) the nitrogen source, and (iii) mixing and aeration in a stirred tank bioreactor. ECM containing 13.33 and 20 g/L of reducing sugars reached a biomass production of 1.75 and 2.22 gDCW/L, respectively. The biomass yield from ECM was at least 2.5-fold higher than that obtained using Luria-Bertani Broth (LB) medium (0.23 vs 0.09). In addition, the growth rate increased with the agitation velocity (0.44 h -1 at 200 rpm; 0.36 h -1 at 150 rpm). Our findings suggest that avocado seeds represent a cost-effective material for producing a sustainable culture medium for bacterial growth of E. coli and other strains of interest in biotechnological processes.

Agroindustry residues can be used to produce valuable chemicals such as lactic acid, which is a primary chemical platform with many industrial applications. Biotechnological processes are the main approach of lactic acid production; however, culture media has an important impact on their costs. As a result, researchers are exploring various methods of production that use residual or waste biomass as raw materials, most of which are rich in lignocellulose. Nevertheless, starch and micronutrients such as those contained in avocado seeds stand out as promising feedstock for the bioprocess as well. In this study, the lactogenic Escherichia coli strain JU15 was evaluated for producing D-lactate using an avocado seed hydrolysate medium in a controlled stirred-tank bioreactor. The highest lactic acid concentration achieved was 37.8 g L −1 using 120 g L −1 as the content of initial reducing sugars. The results showed that D-lactate can be produced from avocado seed, which hydrolysates to 0.52 g L −1 h −1 using the engineered E. coli JU15. This study may serve as a starting point to further develop bioprocesses for producing metabolites using avocado seed hydrolysates.

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