Abstract

Near-infrared (NIR) spectroscopy has been developed as a noninvasive tool for the direct, real-time monitoring of glucose, lactic acid, acetic acid, and biomass in liquid cultures of microrganisms of the genera <i>Lactobacillus</i> and <i>Staphylococcus</i>. This was achieved employing a steam-sterilizable optical-fiber probe immersed in the culture (In-line Interactance System^®). Second-derivative spectra obtained were subjected to partial least-squares (PLS) regression and the results were used to build predictive models for each analyte of interest. Multivariate regression was carried out on two different sets of spectra, namely whole broth minus the spectral subtraction of water, and raw spectra. A comparison of the two models showed that the first cannot be properly applied to real-time monitoring, so this work suggests calibration based on non-difference spectra, demonstrating it to be sufficiently reliable to allow the selective determination of the analytes with satisfactory levels of prediction (standard error of prediction (SEP) < 10%). Direct interfacing of the NIR system to the bioreactor control system allowed the implementation of completely automated monitoring of different cultivation strategies (continuous, repeated batch). The validity of the in-line analyses carried out was found to depend crucially on maintaining constant hydrodynamic conditions of the stirred cultures because both gas flow and stirring speed variations were found to markedly influence the spectral signal.

Rapid detection of carbon-nitrogen ratio for anaerobic fermentation feedstocks using near-infrared spectroscopy combined with BiPLS and GSA

Jinming Liu, Nan Li, Feng Zhen, Yonghua Xu, Wenzhe Li, and Yong Sun
Appl. Opt. 58(18) 5090-5097 (2019)

Fiber-optic differential absorption sensor for accurately monitoring biomass in a photobioreactor

Nianbing Zhong, Qiang Liao, Xun Zhu, and Mingfu Zhao
Appl. Opt. 54(2) 228-235 (2015)

In-fiber Mach–Zehnder interferometer as a promising tool for optical nose and odor prediction during the fermentation process

Renato Luiz Faraco Filho, Felipe Oliveira Barino, João Calderano, Ítalo Fernando Valle Alvarenga, Deivid Campos, and Alexandre Bessa dos Santos
Opt. Lett. 48(15) 3905-3908 (2023)

Rapid, noninvasive concentration measurements of aqueous biological analytes by near-infrared Raman spectroscopy

Andrew J. Berger, Yang Wang, and Michael S. Feld
Appl. Opt. 35(1) 209-212 (1996)

Temperature measurements of turbid aqueous solutions using near-infrared spectroscopy

Naoto Kakuta, Hidenobu Arimoto, Hideyuki Momoki, Fuguo Li, and Yukio Yamada
Appl. Opt. 47(13) 2227-2233 (2008)