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This study aims to valorize of enzymatic corncob hydrolysate (ECH) for biomass and lipid productions via microbial bioconversion by the efficient oleaginous yeast Rhodosporidium paludigenum KM281510. Biomass (5.63 g/L), lipids (3.29 g/L), and lipid content (58% (g/g)) were observed by batch cultivation in shaking flask. The effect of total sugar concentration in ECH, agitation rate, temperature, and initial pH were investigated in both batch and fed-batch cultivations by shaking flask and 3.0 L airlift bioreactor. Biomass, lipids, and lipid content of 27.77 g/L, 20.27 g/L, and 70% (g/g) were obtained with 100 g/L total sugar (68 g/L glucose, 29 g/L xylose, and 3 g/L arabinose), pH 6.5, 25 °C, 6.0 vvm, for 7 days by batch cultivation in bioreactor. Surprisingly, production parameters were improved by fed-batch, wherein these promising high biomass (36.06 g/L), lipid production (25.12 g/L), and lipid productivity (2.52 g/L/d) values were achieved. Moreover, fed-batch cultivation promoted the utilization of xylose (2.5-times) and arabinose (3.4-times) higher than batch cultivation, achieving lipid content (70% (g/g)) with oleic acid (53%). These results would be helpful for understanding the comprehensive utilization of ECH, especially the pentose sugars, for growth and lipogenesis of oleaginous yeast as well as being a qualified biodiesel feedstock.

The new amylolytic oleaginous red yeast, Sporidiobolus pararoseus KX709872, produced both α-amylase (540 ± 0.09 mU/mL) and amyloglucosidase (23 ± 0.00 mU/mL) and showed good ability to directly convert rice residue from canteen waste to biomass and lipids. Effects of medium composition and cultivation conditions on growth and lipid accumulation for strain KX709872 were investigated under shaking flask and upscaling levels. At C : N ratio of 25 : 1, pH 5.45, 22.36°C, and 199.40 rpm for 7 days, volumetric production of biomass and lipids, lipid content, and lipid productivity reached 17.69 ± 0.44, 8.35 ± 0.19 g/L, 49.48 ± 0.41% (w/w), and 1.67 ± 0.11 g/L/day, respectively. Production of lipids was also implemented in 5.0-L stirred tank bioreactor with 2.5 L of optimized medium at 300 rpm and 3.0 vvm for 5 days. Volumetric production of biomass and lipids, lipid content, and lipid productivity were 16.33 ± 0.49, 8.75 ± 0.13 g/L, 56.61 ± 0.04% (w/w), and 2.19 ± 0.03 g/L/day, respectively. Meanwhile, the fatty acids of lipids from strain KX709872 had high oleic acid content (60-62%) which was similar to those of vegetable oils, indicating that these lipids are promising as an alternative biodiesel feedstock. Moreover, the biodiesel derived from lipids of strain KX709872 had properties satisfying the criteria of ASTM D6751 and EN 14214 standards.

Bioconversion of biodiesel-derived crude glycerol into carotenoids and lipids was investigated by a microbial conversion of an oleaginous red yeast Sporidiobolus pararoseus KM281507. The methanol content in crude glycerol (0.5%, w/v) did not show a significant effect on biomass production by strain KM281507. However, demethanolized crude glycerol significantly supported the production of biomass (8.64 ± 0.13 g/L), lipids (2.92 ± 0.03 g/L), β-carotene (15.76 ± 0.85 mg/L), and total carotenoids (33.67 ± 1.28 mg/L). The optimal conditions suggested by central composite design were crude glycerol concentration (55.04 g/L), initial pH of medium (pH 5.63) and cultivation temperature (24.01°C). Under these conditions, the production of biomass, lipids, β-carotene, and total carotenoids were elevated up to 8.83 ± 0.05, 4.00 ± 0.06 g/L, 27.41 ± 0.20, and 53.70 ± 0.48 mg/L, respectively. Moreover, an addition of olive oil (0.5 - 2.0%) dramatically increased the production of biomass (14.47 ± 0.15 g/L), lipids (6.40 ± 0.09 g/L), β-carotene (54.43 ± 0.95 mg/L), and total carotenoids (70.92 ± 0.51 mg/L). The oleic acid content in lipids was also increased to 75.1% (w/w) of total fatty acids, indicating a good potential to be an alternative biodiesel feedstock. Meanwhile, the β-carotene content in total carotenoids was increased to 76.7% (w/w). Hence, strain KM281507 could be a good potential source of renewable biodiesel feedstock and natural carotenoids.

This study aimed to investigate the efficiency of an aerobic sequencing batch reactor (aerobic SBR) in a nonsterile system using the application of an experimental design via central composite design (CCD). The acidic whey obtained from lactic acid fermentation by immobilized Lactobacillus plantarum sp. TISTR 2265 was fed into the bioreactor of the aerobic SBR in an appropriate ratio between acidic whey and cheese whey to produce an acidic environment below 4.5 and then was used to support the growth of Dioszegia sp. TISTR 5792 by inhibiting bacterial contamination. At the optimal condition for a high yield of biomass production, the system was run with a hydraulic retention time (HRT) of 4 days, a solid retention time (SRT) of 8.22 days, and an acidic whey concentration of 80% feeding. The chemical oxygen demand (COD) decreased from 25,230 mg/L to 6,928 mg/L, which represented a COD removal of 72.15%. The yield of biomass production and lactose utilization by Dioszegia sp. TISTR 5792 were 13.14 g/L and 33.36%, respectively, with a long run of up to 180 cycles and the pH values of effluent were rose up to 8.32 without any pH adjustment.

Cheese whey contains a high organic content and causes serious problems if it is released into the environment when untreated. This study aimed to investigate the optimum condition of lactic acid production using the microaerobic sequencing batch reactor (microaerobic SBR) in a nonsterile system. The high production of lactic acid was achieved by immobilized Lactobacillus plantarum TISTR 2265 to generate an acidic pH condition below 4.5 and then to support single-cell protein (SCP) production in the second aerobic sequencing batch reactor (aerobic SBR). A hydraulic retention time (HRT) of 4 days and a whey concentration of 80% feeding gave a high lactic acid yield of 12.58 g/L, chemical oxygen demand (COD) removal of 62.38%, and lactose utilization of 61.54%. The microbial communities in the nonsterile system were dominated by members of lactic acid bacteria, and it was shown that the inoculum remained in the system up to 330 days.