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Waste paper has a potential to serve as renewable feedstock for the biorefineries of fuels, chemicals and materials due to rich in cellulose and its abundance at low cost. In the present study, pretreated waste office paper (WOP) was enzymatically hydrolysed and used for lipid production by Cryptococcus curvatus. The results suggested that the WOP hydrolysate supplemented with ammonium sulphate (2 g/L) and yeast extract (0.5 g/L) as nitrogen source at a C/N ratio of 80 were the most suitable for high yield of lipids. The biomass, lipid yield, lipid content and lipid coefficient achieved from batch cultivation of C. curvatus using untreated and pretreated WOP hydrolysates were 6.32 and 15.20 g/L, 1.39 and 5.75 g/L, 22 and 37.8%, and 99.9 and 234.6 mg/g sugar with the productivity of 0.02 and 0.08 g/L/h, respectively. The fatty acid profile of the lipids indicated that the oleic acid was the major fatty acid followed by palmitic acid, stearic acid and linoleic acid which is quite similar to plant/vegetable oils. Thus, the results suggested that the waste office paper could be an alternative feedstock for production of microbial lipids for biodiesel.

Volatile fatty acids (VFAs) derived from organic wastes are being considered as low-cost feedstock for microbial lipid production as a valuable alternative to plant derived oils/biodiesel. In this study, VFAs were produced from anaerobic open culture fermentation of wastepaper and subsequently, used as a feedstock for lipid production by Cryptococcus curvatus. Total VFAs, yield and productivity achieved from waste office paper (WOP) and waste newspaper (WNP) were 17.3 and 10.2 g/L, 0.17 and 0.10 g/g TS, and 0.86 and 0.51 g/L/day, respectively. Biomass, lipid content and productivity achieved utilizing VFAs derived from WOP and WNP were 4.3 and 2.9 g/L, 41.2 and 27.7% DCW, and 0.037 and 0.033 g/L/h, respectively. The dominance of fatty acids such as oleic, palmitic, stearic and linoleic acid in the lipids suggests a high level of similarity with plant/vegetable oils used for biodiesel production. Therefore, VFAs derived from wastepaper could be potentially used as feedstock to produce microbial lipids towards cost-effective production of biodiesel.

A simple hydrodynamic cavitation (HC) system was newly employed as a pretreatment method for H 2 production from cheese whey. This system offered not only the sonication effect but also an increase in the temperature of the solution. With HC pretreatment for 15 min, a higher H 2 production yield (1.89 mol H 2 /mol lactose) was obtained than with other conventional pretreatment methods such as heating and sonication. HC pretreatment efficiency was synergistically increased when combined with alkaline conditions. In this way, the amount of solubilized nutrient was greatly increased and methanogens were completely removed, leading to H 2 gas of higher purity (48%) and a yield of 3.30 mol H 2 /mol lactose. HC pretreatment under alkaline conditions can be used to efficiently pretreat organic-rich wastewater, including cheese whey, without any scale-up problem, and is an excellent pretreatment option for H 2 production.

This research explores the application of glucose and xylose from corn stover pretreated with nitric acid (HNO3) for the co-production of bioethanol and biodiesel. Response surface methodology was employed to optimize HNO3 pretreatment condition including HNO3 concentration (0.2–1.0%), temperature (140–160 °C), and reaction time (1–10 min). The optimal reaction condition was 151.9 °C, 0.68% HNO3 and 2.5 min, which resulted in the highest xylose yield of 77.8% and glucan content of 57.1%. Quasi-simultaneous saccharification and fermentation (Q-SSF) of pretreated corn stover with Saccharomyces cerevisiae gave an ethanol concentration of 22.4 g/L, corresponding to 69.1% theoretical ethanol yield based on initial cellulose weight. In addition, Cryptococcus curvatus in hydrolysate medium showed the lipid yield (final cell weight × lipid content) of 1.04 g/L, which was higher than those in defined medium using pure xylose. Our work demonstrates that the simultaneous production of ethanol and lipid can be one potentially promising option for lignocellulose-derived fuel production.

Biodiesel produced from oleaginous microorganisms shows promise in displacing use of petroleum diesel fuel, however, low biodiesel yields and rigorous processing have thwarted large-scale commercialization. Here, we report a simple and efficient two-step process for generating biodiesel blends from microbial biomass, which eliminates the need for solvent extractions, distillations, or additional purifications. In the present work, diesel fuel was utilized to extract biodiesel produced from direct transesterification of the yeast, Cryptococcus curvatus , and microalgae, Scenedesmus dimorphus , thus generating a blend of microbial biodiesel and diesel fuel. Up to 93% and 83% of the produced biodiesel is extracted from both yeast and microalgae, respectively, whereas the majority of pigments are excluded. A B20 blend produced from yeast meets key ASTM fuel requirements including flash point, viscosity, sulfur, oxidation stability, and acid number. Integration of experimental data into system models reveals a 25% reduction in the net energy ratio (NER) with the process presented here compared to traditional solvent extraction.