Production of Raw Starch-Digesting Amylolytic Preparation in Yarrowia lipolytica and Its Application in Biotechnological Synthesis of Lactic Acid and Ethanol

Production, characterization, and bio-ethanologenic potential of a novel tripartite raw starch-digesting amylase from Priestia flexa UCCM 00132

The biological conversion of agro-waste biomass into value-added metabolites is one of the trendy biotechnological research areas in recent times. One of the major drawbacks of the bioprocess is the saccharification potential of the amylolytic enzyme that releases reducing sugar from complex biomass to serve as substrate for fermentation. The present study reports the production of a novel tripartite raw starch-digesting amylase (RSDA) by an indigenous Priestia flexa strain with α-, β-, and gluco-amylolytic activities and its potential for bioethanol production. Response surface statistics was employed to develop a suitable medium for improved production of the tripartite enzyme by submerged fermentation. The bioprocess selected raw starch (4.36%) Ca2+(2.71 g/L) and Zn2+ (0.0177 g/L) as significant variables which demonstrated a total RSDA activity of 7208.23 U/mL in a 5-L batch bioreactor. SDS/Native-PAGE determined the molecular weights of the 27-fold purified product as 25.2 kDa, 57.3 kDa, and 90.1 kDa for α-, β-, and gluco-amylases, respectively. Optimum temperature and pH for enzyme activity were respectively broad at 30-70 °C and 4-11. The enzyme mixture demonstrated digestibility above 90% against a variety of raw starches and simultaneous fermentation of digestate with Saccharomyces cerevisiae generated 71.69 g/L of bioethanol within 24 h suggesting great potential for bioethanologenesis.

Identification of Cellulose-Degrading Bacteria and Assessment of Their Potential Value for the Production of Bioethanol from Coconut Oil Cake Waste

Bioconversion of lignocellulosic biomass is a highly promising alternative to rapidly reduce reliance on fossil fuels and greenhouse gas emissions. However, the use of lignocellulosic biomass is limited by the challenges of efficient degradation strategies. Given this need, Bacillus tropicus (B. tropicus) with cellulose degradation ability was isolated and screened from rotten dahlia. The strain efficiently utilized coconut oil cake (COC) to secrete 167.3 U/mL of cellulase activity. Electron microscopy results showed significant changes in the structure and properties of cellulose after treatment with B. tropicus, which increased the surface accessibility and the efficiency of the hydrolysis process. The functional group modification observed by Fourier transform infrared spectroscopy indicated the successful depolymerization of COC. The X-ray diffraction pattern showed that the crystallinity index increased from 44.8% to 48.2% due to the hydrolysis of the amorphous region in COC. The results of colorimetry also reveal an efficient hydrolysis process. A co-culture of B. tropicus and Saccharomyces cerevisiae was used to produce ethanol from COC waste, and the maximum ethanol yield was 4.2 g/L. The results of this work show that B. tropicus can be used to prepare biotechnology value-added products such as biofuels from lignocellulosic biomass, suggesting promising utility in biotechnology applications.

Nutrient biomass production from agro-industrial residues using Yarrowia lipolytica: screening and optimization of growing conditions

Abstract The possibility of using agro-industrial residues in bioconversion processes advances with the development of biotechnology and the search for processes in which is possible to add commercial value to previously discarded products. These processes should be low cost, easy to control and chemical-free. The yeast Yarrowia lipolytica (YL) is widely used to produce lipids, enzymes, citric acid, and proteins, among others. This study aimed to evaluate the capacity of this yeast to use agro-industrial residues as a source of carbon without adding extra carbohydrate sources for the development of cells. The study evaluated the production of proteins and lipids from different carbon sources as well as the optimization of the process (agitation, temperature, and nitrogen source). Indeed, YL produced 22.3% of protein and 9.4% of lipids in dry biomass, a 179% of protein and 660% of lipid increase from raw material, respectively, when using cassava residues as a carbon source. However, lipase production was low, indicating that the strain had priority for cell growth.

Hydrolytic secretome engineering in Yarrowia lipolytica for consolidated bioprocessing on polysaccharide resources: review on starch, cellulose, xylan, and inulin

Consolidated bioprocessing (CBP) featuring concomitant hydrolysis of renewable substrates and microbial conversion into value-added biomolecules is considered to bring substantial benefits to the overall process efficiency. The biggest challenge in developing an economically feasible CBP process is identification of bifunctional biocatalyst merging the ability to utilize the substrate and convert it to value-added product with high efficiency. Yarrowia lipolytica is known for its exceptional performance in hydrophobic substrates assimilation and storage. On the other hand, its capacity to grow on plant-derived biomass is strongly limited. Still, its high potential to simultaneously overproduce several secretory proteins makes Y. lipolytica a platform of choice for expanding its substrate range to complex polysaccharides by engineering its hydrolytic secretome. This review provides an overview of different genetic engineering strategies advancing development of Y. lipolytica strains able to grow on the following four complex polysaccharides: starch, cellulose, xylan, and inulin. Much attention has been paid to genome mining studies uncovering native potential of this species to assimilate untypical sugars, as in many cases it turns out that dormant pathways are present in Y. lipolytica's genome. In addition, the magnitude of the economic gain by CBP processing is here discussed and supported with adequate calculations based on simulated process models. KEY POINTS: • The mini-review updates the knowledge on polysaccharide-utilizing Yarrowia lipolytica. • Insight into molecular bases founding new biochemical qualities is provided. • Model industrial processes were simulated and the associated costs were calculated.