A solid vegetable waste stream was subjected to dilute acid (HCl) pretreatment with the goal of converting the waste into a form that is amenable to biochemical processes which could include microbial lipids, biohydrogen, and volatile organic acids production. Specifically, this study was conducted to identify the most suitable pretreatment condition that maximizes the yield or concentration of sugars while minimizing the production of compounds which are inhibitory to microbes (i.e., furfural, hydroxymethylfurfural, and organic acids). Temperatures from 50–150 °C and HCl loading from 0–7 wt % were studied to using an orthogonal central composite response surface design with eight center points. The effects of the variables under study on the resulting concentrations of sugars, organic acids, and furans were determined using the quadratic response surface model. Results indicated that the biomass used in this study contains about 5.7 wt % cellulose and 83.8 wt % hemicellulose/pectin. Within the experimental design, the most suitable pretreatment condition was identified to be at 50 °C and 3.5 wt % HCl. A kinetic study at this condition indicated process completion at 30 mins. that produced a hydrolyzate that contains 31.30 ± 0.44 g/L sugars and 7.40 ± 0.62 g/L organic acids. At this condition, a yield of ~0.47 g sugar/g of dry solid vegetable waste was obtained. The absence of furans suggests the suitability of the resulting hydrolyzate as feedstock for biochemical processes. The results suggested that the sugar concentration of the pretreated biomass is highly affected by the presence of other compounds such as amines, amino acids, and proteins. The effect however, is minimal at low levels of HCl where the highest total sugar production was observed.

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Lactic acid, an important commodity chemical for various applications, is mainly produced through fermentation. In this study, the potential of non-ionic surfactants (an alcohol ethoxylate (AE) and two alcohol alkoxylates (AAs)) as solvents for the extraction of lactic acid from aqueous solutions is reported for the first time. Ternary mixtures containing lactic acid, water, and surfactants were prepared for the assessment. The results indicated that for all the systems, the water–surfactant binary pair exhibits partial immiscibility. Furthermore, the results suggested that with respect to the size of the two-phase region and stability of phases developed, the AE is the suitable solvent for the targeted extraction process. Thus, tie-lines for the system lactic acid + water + AE were then determined to establish the phase diagram of the system at 308.15 K. From the tie-lines, distribution coefficients and separation factors were estimated, which indicated that a compromise between the size and number of extraction units is necessary if AE is to be used as a solvent for lactic acid extraction. The extraction efficiency was estimated to be only about 37–48%. Nevertheless, the biodegradability and non-toxicity of AE makes it a viable solvent for the development of the extractive lactic acid fermentation process.