Abstract
Lactic acid (LA) was produced on a pilot scale using a defined medium with glucose, acid whey, sugar bread and crust bread. The fermentation broths were then subjected to micro- and nanofiltration. Microfiltration efficiently separated the microbial cells. The highest average permeate flow flux was achieved for the defined medium (263.3 L/m2/h) and the lowest for the crust bread-based medium (103.8 L/m2/h). No LA losses were observed during microfiltration of the acid whey, whilst the highest retention of LA was 21.5% for crust bread. Nanofiltration led to high rejections of residual sugars, proteins and ions (sulphate, magnesium, calcium), with a low retention of LA. Unconverted sugar rejections were 100% and 63% for crust bread and sugar bread media respectively, with corresponding LA losses of 22.4% and 2.5%. The membrane retained more than 50% of the ions and proteins present in all media and more than 60% of phosphorus. The average flux was highly affected by the nature of the medium as well as by the final concentration of LA and sugars. The results of this study indicate that micro- and nanofiltration could be industrially employed as primary separation steps for the biotechnologically produced LA.
Highlights
Bio-based production of platform chemicals from renewable resources is currently a topic of intensive research
The aim of this study is to demonstrate the efficient separation of lactic acid from different fermentation broths
When a defined medium with glucose as the single carbon source was utilized, fermentation lasted for 48 h, resulting in 99.5 g/L of lactic acid with the strain A20 (Figure 2A)
Summary
Bio-based production of platform chemicals from renewable resources is currently a topic of intensive research. Lactic acid is an important bulk chemical with a global market of 1220.0 kt in [1]. Lactic acid can be produced biotechnologically from various renewable resources and waste streams such as food waste [3,4,5], mixed bakery waste [6], coffee pulp and mucilage [7,8], algal biomass [9], and lignocellulosic hydrolysates [10] among others. The utilization of waste and by-product streams as alternative fermentation substrates could reduce the cost of the upstream process of bulk chemicals and, at the same time, their production would not compete with food and feed. Renewable materials like lignocellulosic biomass result in an undefined medium, rendering the downstream process of organic acids more complicated
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