A Unique Bacterial Pelletized Cultivation Platform in Rhodococcus opacus PD630 Enhanced Lipid Productivity and Simplified Harvest for Lignin Bioconversion

Abstract

Pelletized liquid cultivation has been widely explored because of its advantages in biomanufacturing, such as easier biomass harvesting, higher product yield, and lower medium viscosity and energy consumption. In this study, we discovered that the nonfilamentous bacterium Rhodococcus opacus PD630 could form pellets during the fermentation of alkaline pretreatment liquor containing lignin as a carbon source. This discovery advanced our understanding of bacterium pelletization, as only filamentous fungi and filamentous bacteria were reported to form pellets without the addition of external agents such as flocculants or polymers in previous research. Several factors were investigated to understand how they affect the process of pelletization. Notably, the lipid content in the pellets was much higher than in the scattered bacteria at low nitrogen concentration (<0.5 g/L), under which condition (high carbon to nitrogen ratio) the industrial microbial production for lipids was carried out. Moreover, the highest pellet percentage (∼60% of the total biomass) was observed at 30 g/L soluble solid content, an agitation rate of 180 rpm, 1.4 g/L NH4NO3, an initial optical density (OD600) of 10, and a centrifugation speed of 6000 rpm. The study also opens new avenues to decrease harvesting and cultivation cost as well as energy consumption for microbial fermentation.

Production of carotenoids from aromatics and pretreated lignocellulosic biomass by Novosphingobium aromaticivorans

“…The method used to generate the sorghum APL feedstock is well known to solubilize easily cleavable aromatics from plant cell walls, without the breakdown of the carbohydrate and lignin polymers in the biomass ( 28 ). We showed that N. aromaticivorans can grow in the presence of sorghum APL alone, unlike previous studies which have supplemented lignocellulosic APL with minerals ( 38 – 43 ) and/or nitrogen/carbon sources ( 38 , 40 , 44 , 45 ). We also found that N. aromaticivorans produces nearly the same amounts (normalized to dry cell weight) of carotenoids and CoQ 10 when grown on sorghum APL as when grown in a defined medium containing vanillate ( Fig.…”

Recent Biotechnology Advances in Bio-Conversion of Lignin to Lipids by Bacterial Cultures

“…Pelleted culture has been extensively studied for its high yield and ease of product collection, the low viscosity of the medium, and thus low energy consumption ( Nair et al, 2016 ). Xu et al (2022) reported for the first time the spontaneous formation of pellets by bacteria during fermentation with an alkaline treatment solution of maize stover as the carbon source, even in the absence of added chemical coagulants. It was found that the lipid content of the pellets was higher than that of the suspended biomass at low nitrogen concentrations.…”