Combined use of sugars and nutrients derived from young maize plants for thermophilic l-lactic acid fermentation

Abstract

Fermentation of lignocellulosic biomass requires auxiliary materials such as nutrients for fermentation. Because of the low prices of fermentation products such as bioethanol, the costs of nutrients are not negligible. We have developed the concept of using substances natively present in lignocellulosic biomass as nutrients for the downstream fermentation. The leaves and stalks of young dent corn plants were used as biomass and the nutrients were recovered by soaking them in water before alkaline pretreatment, followed by enzymatic saccharification and fermentation. Performing thermophilic L-lactic acid fermentation using these recovered nutrients support their use as commercially feasible alternatives. A level of recovered nutrients of 40% was sufficient to support the fermentation of recovered sugars derived from the same corn biomass. However, the amount of recovered nutrients required for fermentation was almost double that when using yeast extract based on the amounts of nitrogen and/or phosphorus added. The nitrogen and phosphorus balances in the process indicated that adding nutrients was crucial for promoting fermentation based on the amounts of nitrogen and phosphorus. The nutrients proposed were considered to be effective for fermenting biomass pretreated by alkaline, dilute acid, and hydrothermal methods.

Lactic acid production on a combined distillery stillage and sugar beet molasses substrate

“…It can be concluded that an optimal value of C/N ratio varies significantly and thus could not be considered as a crucial parameter for the evaluation of media. Assuming that the sugars from molasses contain on average 40% of C, the value of C/N ratio in the stillage/molasses media was in the range 13 to 23 and corresponded well with the reported values …”

“…noticed diauxic growth in fermentation performed on canned pineapple syrup by Lactococcus lactis at 20 g L −1 of initial sugar concentration. In that study, diauxic growth considerably extended the fermentation time up to 55.5 h, which finally resulted in a very low productivity …”

“…Also, a faintly noticeable lag phase implies that the initial composition of stillage/molasses media was appropriate for LAB growth. Many studies have shown that carbon/nitrogen (C/N) ratio considerably influences LA yield and cell growth . In the study of Akao et al .…”

“…Many studies have shown that carbon/nitrogen (C/N) ratio considerably influences LA yield and cell growth . In the study of Akao et al . sufficient C/N ratio for LA fermentation was in the range from 27 to 35.…”

Saccharification of biopretreated paddy straw with indigenous holocellulase and fermentation with Saccharomyces cerevisiae LN1 under optimized conditions

“…Similar results were obtained in a study by Castro and Roberto (2015) during saccharification and fermentation of dilute acid pretreated rice straw by thermotolerant yeast Kluyveromyces marxianus NRRL Y-6860. Among the evaluated strategies, similar ethanol yields were recorded with or without nutrient addition confirming the observation that hydrolysate must be containing sufficient nutrients to sustain metabolic activity of yeast during fermentation (Akao et al 2015). Analysis of hydrolysate also reveals the presence of sufficient macro and micro nutrients.…”